Abstract: An impact body adapted for being mounted to a transmission module is provided. The transmission module includes a rotation portion formed with a receiving space and an axle disposed in the receiving space. The impact body is pivotally mounted to the rotation portion and received in the receiving space. A protrusion integrally extends outwardly from the other side of the impact body to allow the impact body swings around the protrusion. Whereby, the transmission module is easy to produce and assemble, has a lighter weight or greater rotary output power, and can improve transmission efficiency and lifetime, thus resulting in great inventive effects for use.