A clutch device (10) for an automatic speed changer has a clutch drum (16), first and second friction engagement elements (12, 14) supported by the clutch drum (16), a first piston (18) provided so as to be axially movable on the outer peripheral side of the clutch drum (16) and making the first friction engagement element (12) engage, and a second piston (20) provided so as to be axially movable on the inner peripheral side of the clutch drum (16) and making the second friction engagement element (14) engage. The clutch drum (16) is constructed from an inner drum section (26) welded to an input shaft (22) and an outer drum section (30) welded to the inner drum section (26) and supporting the first friction engagement element (12) and the second friction engagement element (14). The first piston (18) is axially slidable relative to the inner drum section (26), and the second piston (20) is axially slidable relative to the input shaft (22). By the above structure, the clutch device (10) can be reduced in size. |