PURPOSE: To establish a transmission system to the second speed, by separating an oil way combining the first and the second shift valves into an upper stream side oil way linking to the first shift valve and a lower stream side oil way linking to the second shift valve, and connecting the both oil ways at an automatic shift position.

CONSTITUTION: When a manual valve 9 is at the D position, the first oil way L1 linking to an oil pressure source 8 is connected to the second oil way 12 linking to the first shift valve 101, the pressure oil of a specific line pressure is fed, and the oil feeding to the first speed hydraulic clutch C1 through the third oil way L3, and the oil feeding to the second speed to the 4th speed hydraulic clutches C2 to C4 are performed. That is, since the first shift valve 101 is converted to the first speed and the second speed positions, the second shift valve 102 is converted to the second speed and the third speed positions, and the third shift valve 103 is converted to the third speed and the 4th speed positions, the modulator pressure of the first oil way L1 is input to oil chamber 101a and 102a at the right ends of the first and the second shift valves 101 and 102, an oil chamber 101b at the left end of the first shift valve 101, and an oil chamber 103a at the right end of the third shift valve 103.