A device and method for detecting the number of revolutions of a sensorless electric park brake (EPB) motor. The device for detecting the number of revolutions of a sensorless motor includes: an actuator driving motor used to set and release a parking brake of an EPB system; an electronic control module for controlling the motor, a vehicle battery for supplying power to the motor and the electronic control module; and a main processing unit for receiving an output signal of the electronic control module and estimating the number of revolutions of the motor, wherein the electronic control module further includes a ripple measuring unit for receiving an output signal of the motor and measuring a ripple of the motor.