To increase the rigidity of a float member for causing a plurality of torsion springs to operate in series by a simple structure, in a lockup device for a torque converter.

The lockup device is provided with a piston 30 which can be coupled to a front cover 2, a drive plate 31 coupled to the piston 30, a plurality of outer periphery-side torsion springs 32 to which torque is input from the drive plate 31, a float member 42 which is disposed on the turbine side of the outer periphery-side torsion springs 32 and which causes two outer periphery-side torsion springs 32 to operate in series. The float member 42 has a main body portion 42a and an inner peripheral support portion 42b. The main body portion 42a covers the outer peripheral portions and the turbine-side side portions of the outer periphery-side torsion springs 32. The inner peripheral support portion 42b extends from the main body portion 42a toward the inner periphery side, and is supported by an output-side intermediate member 34.