To provide a novel vitamin D3 derivative useful as atherapeutic agent for osteoporosis.Provided is a vitamin D3 derivative represented by thefollowing formula (1) or a medicinally acceptable solvatethereof:wherein R1 represents a hydrogen atom, an alkyl grouphaving 1 to 6 carbon atoms, an alkylcarbonyloxyalkyl groupwith each alkyl having 1 to 6 carbon atoms, or anarylcarbonyloxyalkyl group with the aryl having 6 to 10carbon atoms and the alkyl having 1 to 6 carbon atoms； R2represents a hydrogen atom or an alkyl group having 1 to 6carbon atoms or, together with the other R2 and the carbonatom to which they are bound to, may form a cyclic alkylgroup having 3 to 6 carbon atoms； R3 represents an alkylgroup having 1 to 6 carbon atoms or, together with the otherR3 and the carbon atom to which they are bound to, may form acyclic alkyl group having 3 to 6 carbon atoms； X representsan oxygen atom or a methylene group； and n represents aninteger of 1 or 2.(see above formula)
