Provision of a compound having an anti-HIV activity, particularly an integrase inhibitory activity.A 4-oxoquinoline compound represented by the following formula [I] or a pharmaceutically acceptable salt thereof: ##STR00001## wherein each symbol is as defined in the specification.The present invention also relates to a pharmaceutical composition containing the 4-oxoquinoline compound or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier; an integrase inhibitor, an antiviral agent, anti-HIV agent, and the like, which contains the 4-oxoquinoline compound or a pharmaceutically acceptable salt thereof as an active ingredient; an anti-HIV composition containing the 4-oxoquinoline compound or a pharmaceutically acceptable salt thereof, and one or more other kinds of anti-HIV activity substances as active ingredients; an anti-HIV agent containing the 4-oxoquinoline compound or a pharmaceutically acceptable salt thereof as an active ingredient, which is used for a multiple drug therapy with other anti-HIV agent(s), and the like.