Abstract: A torque converter 1 is provided with a lockup device 4 having a simplified structure. Damper mechanism 40 has a drive member 54, a driven member 53 and a torsion spring 52. Piston 38 has an inner peripheral surface rotatably and axially movably supported on the outer peripheral surface of the driven member 53. The piston 38 is non-rotatably and axially movably coupled to the front cover 2. The piston 38 has an inner diameter S that is larger than an outer diameter of the damper mechanism 40. The piston 38 is arranged radially outside the damper mechanism 40. A seal ring 67 is disposed between the outer peripheral surface of the driven member 53 and the inner peripheral surface of the piston 38 for sealing spaces on its axially opposite sides from each other.