A piperidine derivative of formula (I) ##STR00001## (wherein all symbols are as described in the specification.) and an intermediate for the preparation thereof. The compound of formula (I) has phosphodiesterase 4 inhibitory activity, and it is useful for the prevention and/or treatment of inflammatory diseases, diabetic diseases, allergic diseases, autoimmune diseases, ocular diseases, osteoporosis, bone fracture, osteoarthritis, obesity, bulimia, depression, Parkinson's disease, dementia, ischemia-reperfusion injury, leukemia, acquired immunodeficiency deficiency syndrome (AIDS), shock, systemically inflammatory responsive diseases (SIRS), etc.