diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index d77f53d..4359bdc 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -58,17 +58,17 @@ jobs:
     - name: Install dependencies in GHA
       run: |
         python -m pip install --upgrade pip
-        pipenv install --deploy --dev
+        pip install -e ".[dev]"
     - name: Lint with pylint
       run: |
-        pipenv run flake8 src/k2hr3client
-        pipenv run mypy src/k2hr3client
-        pipenv run pylint src/k2hr3client
-        pipenv run python3 setup.py checkdocs
+        flake8 src/k2hr3client
+        mypy src/k2hr3client
+        pylint src/k2hr3client
+        python3 setup.py checkdocs
       shell: sh
     - name: Test with unittest
       run: |
-        pipenv run python3 -m unittest discover src
+        python3 -m unittest discover src
       shell: sh
     - name: Install dependencies for upload pypi package
       if: startsWith(github.ref, 'refs/tags')
diff --git a/Makefile b/Makefile
index 4c5aa04..293704c 100644
--- a/Makefile
+++ b/Makefile
@@ -49,11 +49,9 @@ BROWSER := python3 -c "$$BROWSER_PYSCRIPT"
 help:
 	@python3 -c "$$PRINT_HELP_PYSCRIPT" < $(MAKEFILE_LIST)
 
-init:
-	python3 -m pip install pipenv
-	pipenv install --skip-lock
-	pipenv graph
-	pipenv install --dev
+init: ## Install dependencies and development dependencies
+	python3 -m pip install -e .
+	python3 -m pip install -e ".[dev]"
 
 clean: clean-build clean-pyc clean-test ## remove all build, test, coverage and Python artifacts
 
diff --git a/Pipfile b/Pipfile
deleted file mode 100644
index 7bb7e7c..0000000
--- a/Pipfile
+++ /dev/null
@@ -1,30 +0,0 @@
-[[source]]
-name = "pypi"
-url = "https://pypi.org/simple"
-verify_ssl = true
-
-[dev-packages]
-coverage = "*"
-flake8 = "*"
-flake8-docstrings = "*"
-pep8-naming = "*"
-pycodestyle = "*"
-mccabe = "*"
-sphinx-autoapi = "*"
-sphinx-intl = "*"
-sphinx-rtd-theme = "*"
-sphinx = "*"
-watchdog = "*"
-wheel = "*"
-twine = "*"
-pylint =  "*"
-astroid = "*"
-mypy = "*"
-"collective.checkdocs" = "*"
-tomli = "*"
-dill = "*"
-
-[packages]
-requests = "*"
-urllib3 = "*"
-setuptools = "*"
diff --git a/README.rst b/README.rst
index 76ed7b9..38641fa 100644
--- a/README.rst
+++ b/README.rst
@@ -133,7 +133,6 @@ Development
 Clone this repository and go into the directory, then run the following command::
 
     $ make init
-    $ pipenv shell
     $ make lint test docs build
 
 
diff --git a/pyproject.toml b/pyproject.toml
index 354d21a..cd5a9d7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "k2hr3client"
-dynamic = ["version"]
+version = "1.1.3"
 requires-python = ">=3.9"
 authors = [
   {name = "Hirotaka Wakabayashi", email = "hiwakaba@lycorp.co.jp"},
@@ -29,6 +29,34 @@ classifiers = [
   'Programming Language :: Python :: 3',
   'Programming Language :: Python :: 3.9',
 ]
+dependencies = [
+  "requests",
+  "urllib3",
+  "setuptools",
+]
+
+[project.optional-dependencies]
+dev = [
+  "coverage",
+  "flake8",
+  "flake8-docstrings",
+  "pep8-naming",
+  "pycodestyle",
+  "mccabe",
+  "sphinx-autoapi",
+  "sphinx-intl",
+  "sphinx-rtd-theme",
+  "sphinx",
+  "watchdog",
+  "wheel",
+  "twine",
+  "pylint",
+  "astroid",
+  "mypy",
+  "collective.checkdocs",
+  "tomli",
+  "dill",
+]
 
 [project.urls]
 Homepage = "https://github.com/yahoojapan/k2hr3client_python"
diff --git a/setup.py b/setup.py
index 17cfe50..9130726 100644
--- a/setup.py
+++ b/setup.py
@@ -52,28 +52,8 @@
 # Always prefer setuptools over distutils
 from setuptools import setup
 
-
-def get_version():
-    """Returns the package version from __ini__.py."""
-    from pathlib import Path
-    from os import path, sep
-    import re
-
-    here = path.abspath(path.dirname(__file__))
-    init_py = Path(sep.join([here, 'src', 'k2hr3client', '__init__.py'])).resolve()
-
-    with init_py.open() as fp:
-        for line in fp:
-            version_match = re.search(r"^__version__ = ['\"]([^'\"]*)['\"]",
-                                      line.strip(), re.M)
-            if version_match:
-                return version_match.group(1)
-    raise RuntimeError('version expected, but no version found.')
-
-
-setup(
-    version=get_version(),
-)
+# All configuration is now in pyproject.toml
+setup()
 
 #
 # Local variables:
diff --git a/src/k2hr3client/__init__.py b/src/k2hr3client/__init__.py
index 129cfba..680518d 100644
--- a/src/k2hr3client/__init__.py
+++ b/src/k2hr3client/__init__.py
@@ -22,14 +22,23 @@
 """K2HR3 Python Client of Token API."""
 
 __author__ = 'Hirotaka Wakabayashi <hiwakaba@lycorp.co.jp>'
-__version__ = '1.1.3'
 
 import configparser
 import logging
-from logging.handlers import TimedRotatingFileHandler
+import sys
+from importlib.metadata import PackageNotFoundError, \
+    version as get_version_info
 from logging import StreamHandler
+from logging.handlers import TimedRotatingFileHandler
 from pathlib import Path
-import sys
+
+from k2hr3client import version  # noqa: F401
+
+
+try:
+    __version__ = get_version_info("k2hr3client")
+except PackageNotFoundError:
+    __version__ = "unknown"
 
 LOG = logging.getLogger(__name__)