Documentation for JIRA 5.0. Documentation for other versions of JIRA is available too.
The default language is set by your JIRA administrator (see Configuring JIRA Options), but you can personalise your JIRA account to use a language of your choice.
To choose a language:
「言語」ドロップダウンメニューで特定の言語が利用できない場合、JIRA システム管理者に連絡して、利用したい特定の JIRA 用言語パックをインストールするようリクエストします。
For more information, see Translating JIRA and if necessary, ask your JIRA System Administrator to refer to the Managing JIRA's Plugins page for instructions on how to install JIRA plugins (including JIRA language packs).