A tablet cassette that inhibits rotation of a rotor when the tablet cassette is not mounted. A plurality of engaged portions are provided, about the axial line of a rotary shaft at predetermined intervals in the circumferential direction on an annular inner surface region of a bottom wall portion located a predetermined distance away from the rotary shaft. A sliding shaft is disposed in the rotary shaft, slidable in the axial direction, such that the sliding shaft rotates together with the rotary shaft. The rotary shaft is displaced toward a rotor body when the rotary shaft is coupled to a drive shaft and the rotary shaft is displaced toward a bottom wall portion when the rotary shaft is not coupled to the drive shaft. Two or more engaging portions are provided on arm portions provided on the sliding shaft and engage with some of a plurality of engaged portions.