[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.提供一種具有腸磷酸鹽轉運子(NPT-IIb)抑制作用且可用作為高磷酸鹽血症之治療及/或預防劑的活性成分之化合物。本發明人對具有NPT-IIb抑制作用且可用作為高磷酸鹽血症之治療及/或預防劑之活性成分的化合物進行研究。結果,產生一種具有NPT-IIb抑制作用的經胺基烷基取代之N-噻吩基苯甲醯胺衍生物,因而完成本發明。本發明之經胺基烷基取代之N-噻吩基苯甲醯胺衍生物具有NPT-IIb抑制作用且可用作為高磷酸鹽血症之治療及/或預防劑。