The invention provides a glucitol derivative having the function of reducing a blood sugar level and having preferable properties required of medicines, such as long-lasting drug activity, metabolic stability and security; and a pharmaceutical composition for use in the prevention or treatment of diseases attributable to hyperglycemia, such as diabetes, for example insulin-dependent diabetes (diabetes I), non-insulin-dependent diabetes(diabetes II), complications of diabetes, and obesity. The derivative is a compound represented by the formula (I): wherein m is an integer selected among 1-3; R<1>, R<2>, R<3> and R<4> each independently are optionally hydrogen, substituted C1-C6 alkyl, substituted C7-C14 aralkyl; Ar<1> is optionally substituted naphthyl; and A is optionally heteroaryl substituted by one or more Rb; fused ring may be formed by the heteroaryl together with aromatic carbocycle or aromatic heterocyclyl ring, but in the case that A is benzo-fused ring including 2 or more ring, the radical -(CH1)m is connected to heterocyclyl ring of A; a prodrug of the compound, or a pharmaceutically acceptable salt of either. Also provided are a medicine, a medicinal composition, andthe like each containing the compound.