To suppress shifting shock, improve shifting feeling, and show fail-safe function over all driving areas by composing a hydraulic pressure distribution means for supplying hydraulic pressure to frictional elements of a high/low pressure valve, a rear clutch releasing valve, fail-safe valve and the like.

A control valve 10 is operated for constantly adjusting supplied pressure to a torque converter 2. A damper clutch control valve 12 is operated for improving power transmission efficiency to the torque converter 2. A hydraulic pressure distribution means distributes the hydraulic pressure properly to frictional elements in relation to respective shift position. The hydraulic pressure distribution means is composed of a 1-2 shift valve 34, a 2-3/4-3 shift valve 40, a control switch valve 42, a high/low pressure valve 44, a rear clutch releasing valve 46 and a fail-safe valve 48. The third speed is held when a transmission controlling unit is impossible.