PURPOSE: To reduce a speed change shock by controlling, at the time of speed change to a low-speed side, the operating moment of a speed change mechanism in accordance with a vehicle speed signal and a throttle opening, and making the rotation speed of an output shaft of an automatic transmission approximate to the revolution speed of an engine at the time when the speed change is completed.

CONSTITUTION: When, in an automatic transmission of forward 3 speed stage, and backward 1 speed stage, change in speed from 3rd speed stage to a 2nd speed stage for example is determined in accordance with a vehicle speed signal from a vehicle speed sensor 12 and a throttle opening signal from a throttle sensor 13, a speed change instruction to shift solenoids A, B is issued whereupon the speed is first changed to 1st speed stage. Then, comparison is made between a set value of 1st speed retention time period and an actual retention time period by use of a vehicle speed signal from the vehicle speed sensor 12 and a throttle opening signal from the throttle sensor 13. If the actual retention time period already reaches the set value, a speed chance instruction signal is generated to the shift solenoid B whereupon change to the 2nd speed stage is completed. During 1st speed retention time period as well, the vehicle speed signal and the throttle opening signal retention are always monitored whereby an adequate 1st speed time period is ensured in case the throttle opening is varied too.