When the power transmitting path in an automatic shifting portion (20) is interrupted, a Co-lock control is executed to allow a differential portion (11) to be placed in a non-differential or nearly non-differential state with rotary elements (RE1 to RE3) kept in a unitary rotation. Thus, an engine (8), a first electric motor (M1) and a second electric motor (M2) rotate at an identical or nearly identical speed. Then, for the purpose of controlling the second electric motor (M2) at a rotation speed below a permit rotation speed, it may suffice for the first and second electric motors (M1) and (M2) to be driven in a direction to lower relevant rotation speeds while monitoring any one of an engine rotation speed, a first-motor rotation speed and a second-motor rotation speed. This allows such a control to be easily executed, thereby preventing the second electric motor from reaching a high speed rotation.