Oil pressure detecting means 150 detects a clutch oil pressure in driving a clutch in its engaging direction against a biasing force of a return spring 12 for normally disengaging the clutch. Stroke end detecting means 140 detects that the clutch has reached a stroke end position where clutch disks are in contact with each other when the amount of change in clutch oil pressure becomes larger than a predetermined value. Clutch control correction amount calculating means 130 calculates a work load generated in the return spring 12 according to the clutch oil pressure detected at the stroke end position and then calculates a control correction amount for the clutch according to the difference between the work load calculated above and a predetermined reference value.