This invention offers isoxazole derivatives represented by the following formula (I) in which R 1 and R 2 each stands for hydrogen, lower alkyl, amino and the like； R 3 stands for substituted or unsubstituted aryl or hetero aryl； R 4 stands for hydrogen or lower alkyl； R 5 stands for substituted or unsubstituted phenyl, furyl and the like； and Y stands for -CH 2 -, -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.
