This invention offers isoxazole derivatives represented by the following formula (I)in which R1 and R2 each stands for hydrogen, lower alkyl, amino and the like； R3 stands for substituted or unsubstituted aryl or hetero aryl； R4 stands for hydrogen or lower alkyl； R5 stands for substituted or unsubstituted phenyl, furyl and the like； and Y stands for —CH2—, —CO—, —O—, —NH— and the like,or pharmaceutically acceptable salts thereof which exhibit excellent p38MAPkinase-inhibiting action with reduced side-effects, and are useful for treating such diseases as chronic rheumatoid arthritis, ulcerative colitis and the like.
