An overload protection device includes a motor, a rotatable shaft, a driven wheel, and a transmission mechanism. The rotatable shaft is meshed with the motor. The rotatable shaft includes a rod and a driving arm. A connection pole is formed on the driving arm. An inner surface of the driven wheel forms a protrusion. A sidewall of the protrusion defines a cutout therein. The transmission mechanism includes a resilient member and two arms rotatably connected on the connecting pole. The transmission mechanism is wedged in the cutout. when the motor is overloaded, the torque applied on the arms by the drive force of the motor becomes greater than the torque applied on the arms by the resilient force of the resilient member, the resilient member can no longer hold the transmission mechanism in a wedge shape, the arms become parallel each other to slide out of the cutout.