Seven forward speeds and three reverse speeds are realized by combining two compound planetary gear sets using three clutches and four brakes, and each shift speed is realized by operating two frictional elements, thereby reducing a capacity of a hydraulic pump and enhancing an efficiency of a hydraulic pressure control by realizing each shift speed by operating two frictional elements. A first shift portion and a second shift portion are disposed on the same shaft axis. The first shift portion includes a first planetary gear set formed as a double pinion planetary gear set and a second planetary gear set formed as a single pinion planetary gear set, and the second shift portion includes a third planetary gear set formed as a single pinion planetary gear set and a fourth planetary gear set formed as a single pinion planetary gear set. The first shift portion is combined by one clutch and two brakes, and the second shift portion is combined by one clutch and two brakes.
