diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index bae7dcb6..4f60c011 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -6,21 +6,14 @@ jobs:
   main:
     strategy:
       matrix:
-        # Python 3.6 is not supported on Ubuntu 22.04
-        os: ['ubuntu-22.04', 'ubuntu-20.04']
-        python-version: ['3.6', '3.9', '3.12']
+        # os: ['ubuntu-22.04']
+        python-version: ['3.9', '3.12']
         sample: [mapper, minsearch, exchange, exchange_mesh, pamc, bayes, transform]
-        exclude:
-          - os: 'ubuntu-22.04'
-            python-version: '3.6'
-          - os: 'ubuntu-20.04'
-            python-version: '3.9'
-          - os: 'ubuntu-20.04'
-            python-version: '3.12'
       fail-fast: false
 
     name: ${{ matrix.sample }} with Python ${{ matrix.python-version }}
-    runs-on: ${{ matrix.os }}
+    runs-on: 'ubuntu-22.04'
+    # runs-on: ${{ matrix.os }}
     timeout-minutes: 10
 
     steps:
diff --git a/README.md b/README.md
index ae9cf831..1633151b 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ It also offers a driver script to solve the problem with predefined optimization
 ### Prerequists
 
 - Required
-  - python >= 3.6.8
+  - python >= 3.9
   - numpy >= 1.14
   - tomli >= 1.2.0
 - Optional
diff --git a/doc/en/source/start.rst b/doc/en/source/start.rst
index c45af938..bf7889a0 100644
--- a/doc/en/source/start.rst
+++ b/doc/en/source/start.rst
@@ -3,7 +3,7 @@ Installation of ODAT-SE
 
 Prerequisites
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Python3 (>=3.6.8)
+- Python3 (>=3.9)
 
     - The following Python packages are required.
         - tomli >= 1.2
@@ -13,7 +13,7 @@ Prerequisites
 
         - mpi4py (required for grid search)
         - scipy (required for Nelder-Mead method)
-        - physbo (>=0.3, required for Baysian optimization)
+        - physbo (>=2.0, required for Baysian optimization)
 
 
 How to download and install
diff --git a/doc/ja/source/start.rst b/doc/ja/source/start.rst
index a34859c0..867aa025 100644
--- a/doc/ja/source/start.rst
+++ b/doc/ja/source/start.rst
@@ -3,7 +3,7 @@ ODAT-SE のインストール
 
 実行環境・必要なパッケージ
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- python 3.6.8 以上
+- python 3.9 以上
 
     - 必要なpythonパッケージ
 
@@ -14,7 +14,7 @@ ODAT-SE のインストール
 
         - mpi4py (グリッド探索利用時)
         - scipy (Nelder-Mead法利用時)
-        - physbo (ベイズ最適化利用時, ver. 0.3以上)
+        - physbo (ベイズ最適化利用時, ver. 2.0以上)
 
 ダウンロード・インストール
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/pyproject.toml b/pyproject.toml
index f5aa41e5..99c8e0bd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -13,7 +13,7 @@ packages = [
   ]
 
 [tool.poetry.dependencies]
-python = ">=3.6.8"
+python = ">=3.9"
 numpy = "^1.14"
 tomli = ">=1.2"
 scipy = {version = "^1", optional = true}