An object of the present invention is to provide a methyllactam ring compound that has an SGLT1 inhibitory activity and is useful for a drug, or a pharmaceutically acceptable salt thereof, a pharmaceutical composition comprising it, and pharmaceutical use thereof. A compound of Formula [I]: or a pharmaceutically acceptable salt thereof, a pharmaceutical composition comprising it, and pharmaceutical use thereof is provided.本發明之目的在於提供一種具有SGLT1抑制活性,可用來作為醫藥之甲基內醯胺環化合物或其製藥上所容許的鹽及含有其等之醫藥組成物以及其等之醫藥用途。本發明提供一種式[I]之化合物或其製藥上所容許之鹽及含有其等之醫藥組成物以及其等的醫藥用途。