An 8-oxoadenine compound useful as an immuno-modulator having specific activity against Th1/Th2, specifically a prophylactic and therapeutic agent for a topical application for allergic diseases, viral diseases and cancers, which is represented by the following formula (1): wherein A is a group of a formula represented by the formula (2): wherein R2 is a substituted or unsubstituted alkyl group and so on, R3 is hydrogen atom or an alkyl group, R is a halogen atom and so on, n is 0˜2, X1 is oxygen atom, Z is straight or branched chain alkylene, and R1 is an alkyl group which is optionally substituted by hydroxy group, an alkoxy group, alkoxycarbonyl group and so on, or its pharmaceutically acceptable salt.