PURPOSE: To make constitution and control easy by processing a vehicle speed signal by means of a filter and using the processed signal for judgement on speed change shocks.

CONSTITUTION: In the case of carrying out speed change control on an automatic transmission, according to a processed signal obtained by processing a vehicle speed signal by means of a band pass filter 36, variation and speed change time in the case of changing speed are detected, so that speed change shocks can be judged easily. Furthermore, when the speed change shocks are generated, since line pressure is adjusted so as to be increased or decreased according to the length of the speed change time, engagement of a speed change clutch 7 can be optimized so that the speed change shocks can be reduced properly.