The objective of the present invention is to provide a compound having inhibitory activity against an intestinal phosphate transporter (NPT IIb) and useful as an active ingredient in a hyperphosphatemia therapeutic agent and/or preventive. A thiophene compound represented by formula (I) may be used as a hyperphosphatemia therapeutic agent and/or preventive having NPT IIb inhibitory activity. (In the formula R each represent H or a lower alkyl or the like L each represent a lower alkyl or the like X represents CH or O X each represent CH or N k is 1 3 and n is 0 1.)