A power transmitting apparatus (20) attached to a crankshaft (56) of an engine (50) includes a clutch motor (30), an assist motor (40), and a controller (80) for controlling the clutch motor (30) and the assist motor (40). When detecting an ignition switch in a starter position, the controller (80) makes a constant current flow through three-phase coils (44) of the assist motor (40) to fix a drive shaft (22) and makes a current flow through three-phase coils (36) of the clutch motor (30) to enable the clutch motor (30) to apply a starter torque TST to the crankshaft (56). This results in cranking the crankshaft (56). Concurrently with the cranking process, fuel injection into the engine (50) and spark ignition are controlled to start the engine (50).