You can restrict who has the ability to change the visibility of repositories in your organization, such as changing a repository from private to public. For more information about repository visibility, see "About repositories."
You can restrict the ability to change repository visibility to organization owners only, or you can allow anyone with admin access to a repository to change visibility.
Warning: If enabled, this setting allows people with admin access to choose any visibility for an existing repository, even if you do not allow that type of repository to be created. 詳しい情報については「Organization でのリポジトリ作成の制限」を参照してください。
-
In the top right corner of GitHub.com, click your profile photo, then click Your organizations.
-
Organizationの隣のSettings（設定）をクリックしてください。
-
In the "Access" section of the sidebar, click Member privileges.
-
[Repository visibility change] の下で、[Allow members to change repository visibilities for this organization] の選択を解除します。
-
[Save] をクリックします。