A base station device and a mobile station device efficiently communicate by using a flexible subframe. When a physical uplink shared channel and a sounding reference signal are not scheduled in a first flexible subframe, and at least the physical uplink shared channel is scheduled in a second flexible subframe immediately following the first flexible subframe, the mobile station device monitors a downlink grant which is used for scheduling the physical downlink shared channel in the first flexible subframe, and receives the physical downlink shared channel except for a last part in a time domain, in the first flexible subframe, based on the detected downlink grant.