Provided is a substituted spiropyrido[1,2-a]pyrazine derivative and pharmaceutically acceptable salt thereof, useful as anti-HIV agent. It is related to a compound represented by the following formula [I] or [II], or its pharmaceutically acceptable salt [Wherein, each symbol represents the same meaning as in the specification].本發明係提供作為抗HIV劑有用的經取代之螺吡啶並[1,2-a]吡衍生物或其製藥上容許之鹽。本發明係關於下述通式[I]或[II]所示化合物或其製藥上容許之鹽[式中,各符號係與說明書中同義]。