PURPOSE: To restrain generation of transmission shock at transmission by carrying out transmission between a high speed stage and a low speed stage through an intermediate speed stage and by carrying out release timing of the intermediate speed stage output corresponding to input axis revolution number.

CONSTITUTION: In case of transmission from a low speed stage to a high speed stage, when simultaneous switching among more than two friction engagement elements is required, first, a shift solenoid 9 is driven by an output signal of an intermediate speed stage forced output means 6 through a driving circuit 8 so as to achieve an intermediate speed stage. And when an output signal that a specific value is added to a value acquired by multiplying an output axis revolution number from a detecting means 1 by an intermediate speed stage gear ratio is put out from an input axis revolution number detecting means 2, a releasing means 7 releases intermediate speed stage forced output, puts out driving signals of the shift solenoids 9 and 10 so as to carry out engagement of friction engagement elements corresponding to the high speed stage and achieves the high speed stage. Thus, generation of transmission shock can be prevented.