To form by a laser a stable and strong welded part through which a support portion of a second transmission claw and a shell of a turbine impeller are joined to each other in a hydraulic power transmission with a lock-up clutch.

In the hydraulic power transmission with a lock-up clutch, a plurality of first transmission claws 33 inserted between adjacent damper springs 32 are securedly provided on a clutch piston 25, and the support portions 34b of a plurality of second transmission claws 34 inserted between the adjacent damper springs 32 while opposing the first transmission claws 33, are joined to an outer peripheral surface of the shell 3s of the turbine impeller 3 through the welded parts 40 formed by the laser L. The welded parts 40 are each formed in a flattened annular shape extending circumferentially along the shell 3s and having at least one cut 41.