To provide a horizontal rotary dryer capable of suppressing occurrence of a fatigue crack in the root part of a support member supporting a heating tube in a rotary dryer body by suppressing deformation of the rotary dryer body in the axial direction during the rotation.

In the horizontal rotary dryer 1, many heating tubes arranged along the axial direction in the cylindrical rotary dryer body 2 are supported by many supporting members projected from the inner surface of the rotary dryer body 2, a material to be dried received from one end of the rotary dryer body 2 is dried by the heat of the heating tubes while being rotated, and the material is discharged from another end. A plurality of reinforcing members 23 arranged along the axial direction of the rotary dryer body 2 are provided to the outer peripheral surface of the dryer body 2 with a fixed interval in the peripheral direction.