PURPOSE: To provide a controller for a spindle motor which controls by a simple logic circuit when the motor is controlled to be stopped.

CONSTITUTION: The control system for a spindle motor comprises a motor l to be controlled, a rotation detector 2 of the motor, a rotating direction controller 3 of the motor, a rotary pulse width monitor 4, a pulse width setter 5, a motor stop trigger generator 6 and a motor rotation stop controller 7. A signal is output by the detector 2 of the motor 1 to be controlled, input to the monitor, and compared to be monitored with a time constant set to the setter 5. A circuit for outputting a reverse control signal at the time of discharging a disk cartridge to brake the motor and stopping the motor by operating the controller 7 by outputting a trigger signal from the generator 6 when the motor is thus decelerated so that the pulse width becomes longer than a set value is provided.