The utility model discloses a side magnetic braking device for a motor, which comprises a rotor, a stator, a machine shell and a wind blade which is fixed on a rotor shaft and is positioned at the back of the machine shell. An armature iron which is fixed on the machine shell is arranged between the machine shell and the wind blade, a spring is arranged between the armature iron and the machine shell and compels the movable end of the armature iron to press the wind blade, and an electromagnet which is corresponding to the position of the armature iron is penetrated on the machine shell. In the device, the inner part of the motor is provided with the braking device which can rapidly stop rotating after a switch cuts off electricity.