To provide a compound which has an excellent activity to modulate the functions of CCR4 or TARC and/or MDC and can be used for the prevention and/or treatment of various inflammatory diseases, allergic diseases, autoimmune diseases and the like.An acylaminopiperidine compound represented by the formula (I) or a pharmaceutically acceptable salt thereof. [Symbols in the formula represent the following meanings; A: a single bond or C1-C6 alkylene, R1: phenyl which may be substituted, etc., R2: —H or C1-C6 alkyl, R3: —H, C1-C6 alkyl or C3-C8 cycloalkyl, R4: pyrrolidin-2-yl which may be substituted, etc., and D: benzene ring or pyrazole ring].