解決:
We redirect the URL / to /about/:
RewriteEngine on
RewriteRule ^/$ /about/ [R]
Note that this can also be handled using the RedirectMatch directive:
RedirectMatch ^/$ http://example.com/about/
Note also that the example rewrites only the root URL. That is, it rewrites a request for http://example.com/, but not a request for http://example.com/page.html. If you have in fact changed your document root - that is, if all of your content is in fact in that subdirectory, it is greatly preferable to simply change your DocumentRoot directive, or move all of the content up one directory, rather than rewriting URLs.
これは、 http://httpd.apache.org/docs/trunk/rewrite/remapping.html#page-headerから取得したソリューションであり、移動された DocumentRoot 見出しを参照してください。