/Applications/MAMP/conf/apacheにあるhttpd.confを開きます。
219〜230行目にある次のコードを探します。
#
# Each directory to which Apache has access can be configured with respect
# to which services and features are allowed and/or disabled in that
# directory (and its subdirectories).
#
# First, we configure the "default" to be a very restrictive set of
# features.
#
<Directory />
Options Indexes FollowSymLinks
AllowOverride None
</Directory>
AllowOverrideのNoneをAllへ変更します。
.htaccessファイルを配置します。
参考:https://stackoverflow.com/questions/7670561/how-to-get-mamp-to-read-htaccess-files