To provide a driving force transmission device having a smaller number of components for efficiently transmitting power from an input shaft to an output shaft, having stable braking performance, and serving as a torque limiting function.

A braking releasing mechanism is formed by utilizing a ball lamp part 7 having a ball 71 for sensing the torque of the input shaft and a ball lamp 72 for storing the ball 71. The ball lamp part 7 consists of an operation converting portion 721 having an inclined face 72a to pressed against the ball 71 during the rotation of the input shaft for converting the rotating torque of the input shaft into motion to cancel the energizing force of a braking mechanism, and a torque limiting portion 722 for storing the ball 71 in the form that the rotating torque cannot converted into the motion to cancel the energizing force when the input shaft receives predetermined or stronger driving force and the ball 71 rides over the inclined face 72a of the operation converting portion 721.