[Problem] To provide a compound that has an intestinal phosphate transporter (NPT-IIb) inhibitory action and is useful as an active ingredient of an agent for treating and/or preventing hyperphosphatemia. [Means for Solution] The present inventors conducted thier studies on a compound that has an NPT-IIb inhibitory action and is useful as an active ingredient of an agent for treating and/or preventing hyperphosphatemia. As a result, they created an aminoalkyl-substituted N-thienylbenzamide derivative which has NPT-IIb inhibitory action, thereby completing the present invention. The aminoalkyl-substituted N-thienylbenzamide derivative of the present invention has an NPT-IIb inhibitory action and can be used as an agent for preventing and/or treating hyperphosphatemia.
