diff --git a/docs/requirements.txt b/docs/requirements.txt
index d2a2b12..c23e22c 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -9,7 +9,7 @@ requests>=2.21.0
 
 # Building Docs requirements
 sphinxjp.themes.basicstrap
-sphinx<6.0
+sphinx<8.0
 sphinx-gallery>0.6.2
 pillow>=7.1.2
 breathe>=4.34.0
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 6fe591c..2e219e7 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -23,7 +23,7 @@ codecov
 
 # doc build
 sphinxjp.themes.basicstrap
-sphinx<6.0
+sphinx<8.0
 sphinx-gallery>=0.6.2
 pillow>=7.1.2  # for sphinx-gallery images
 sphinx_copybutton>=0.3.0