The invention provides a device and a method for measuring cogging torque of a permanent magnet synchronous motor, and belongs to the field of testing of torque of motors. The problems that the existing manual operation method for measuring the cogging torque of a permanent magnet synchronous motor is troublesome in operation and the precision cannot be guaranteed easily are solved. A static torque sensor is connected with a rotor shaft of the measured permanent magnet synchronous motor through a coupling; a direct-current dragging motor is fixed on a second support; a pinion which is meshed with a gearwheel is arranged on an outputting shaft of the direct-current dragging motor; the gearwheel is in clearance fit with the rotor shaft of the measured permanent magnet synchronous motor and is fixedly connected with a shell of the measured permanent magnet synchronous motor; and the shell of the measured permanent magnet synchronous motor is fixedly connected with a stator. The direct-current dragging motor drags the shell of the measured permanent magnet synchronous motor to rotate at a speed of 4-6 rpm/min, the outputting value of the static torque sensor is measured, a measured result is recorded, and data are processed by a LabVIEW software so as to obtain a cogging torque value. The device and the method are used for measuring the cogging torque of the permanent magnet synchronous motor.