A dryer, comprising: a main body having an inner space formed therein; a fixed drum installed in the inner space of the main body, the fixed drum including a front wall having an opening formed therein, a rear wall facing the front wall, and a sidewall, the fixed drum having a non-circular vertical cross section; and a tumbling device coupled to the fixed drum, wherein the tumbling device slides along an inner circumferential surface of the fixed drum as the fixed drum remains stationary to tumble laundry items received in the fixed drum, wherein the tumbling device comprises: a driving motor provided in the inner space; at least one connector having a first end thereof connected to a shaft of the driving motor such that a second end of the connector rotates about the first end thereof as the driving motor rotates the shaft; and a lifter coupled to the second end of the at least one connector, wherein the lifter extends between the front wall and the rear wall of the fixed drum so as to contact the inner circumferential surface of the fixed drum, wherein a length of the at least one connector is variable based on a distance between the shaft of the driving motor and a corresponding portion of the inner circumferential surface of the fixed drum as the lifter slides along the inner circumferential surface thereof such that the lifter maintains contact with the inner circumferential surface of the fixed drum along its non-circular vertical cross section as the driving motor rotates the shaft. a main body having an inner space formed therein; a fixed drum installed in the inner space of the main body, the fixed drum including a front wall having an opening formed therein, a rear wall facing the front wall, and a sidewall, the fixed drum having a non-circular vertical cross section; and a tumbling device coupled to the fixed drum, wherein the tumbling device slides along an inner circumferential surface of the fixed drum as the fixed drum remains stationary to tumble laundry items received in the fixed drum, wherein the tumbling device comprises: a driving motor provided in the inner space; at least one connector having a first end thereof connected to a shaft of the driving motor such that a second end of the connector rotates about the first end thereof as the driving motor rotates the shaft; and a lifter coupled to the second end of the at least one connector, wherein the lifter extends between the front wall and the rear wall of the fixed drum so as to contact the inner circumferential surface of the fixed drum, wherein a length of the at least one connector is variable based on a distance between the shaft of the driving motor and a corresponding portion of the inner circumferential surface of the fixed drum as the lifter slides along the inner circumferential surface thereof such that the lifter maintains contact with the inner circumferential surface of the fixed drum along its non-circular vertical cross section as the driving motor rotates the shaft. a driving motor provided in the inner space; at least one connector having a first end thereof connected to a shaft of the driving motor such that a second end of the connector rotates about the first end thereof as the driving motor rotates the shaft; and a lifter coupled to the second end of the at least one connector, wherein the lifter extends between the front wall and the rear wall of the fixed drum so as to contact the inner circumferential surface of the fixed drum, wherein a length of the at least one connector is variable based on a distance between the shaft of the driving motor and a corresponding portion of the inner circumferential surface of the fixed drum as the lifter slides along the inner circumferential surface thereof such that the lifter maintains contact with the inner circumferential surface of the fixed drum along its non-circular vertical cross section as the driving motor rotates the shaft.