A motor drive device includes: chopping signal generation means for generating a chopping signal Sa when drive current of a driver has reached a first threshold value; chopping signal cut-off means for cutting off the chopping signal Sa when the drive current has reached a second threshold value which is greater than the first threshold value; and overcurrent protection means for generating an overcurrent protection signal Se when the drive current has reached a third threshold value which is greater than the first threshold value and its continuation time has reached a predetermined threshold value time. Thus it is possible to simultaneously obtain the constant current chopping function and the overcurrent protection function and to improve its reliability and safety.