To detect a load of a DC motor compatible with various loads.

A control part 1 which drive-controls a motor 3 includes: a motor drive voltage detection circuit 5; an angular acceleration calculation part 8a connected to a motor rotation sensor 6; an estimated load calculation part 8b which calculates an estimated load being an external load of the motor 3 on the basis of a drive voltage, an angular speed and an angular acceleration; and a determination part 8c which determines that something is caught on the basis of the estimated load. Since the angular speed and the voltage are changed when the external load is applied, the external load can be calculated as the estimated load by using an estimated load calculation formula in which coefficients of items are properly defined, and thus whether something is caught or not can quickly and surely be determined. In particular, the estimated load of a soft material caught at a power window can accurately be calculated by including a viscosity coefficient of an internal load of the motor into a rotation speed change item.