The present disclosure provides a transmission assembly and an office machine comprising the same. The transmission assembly includes a body, a first roller, a second roller, a flexible element, a third roller and a transmission element. The first roller is pivoted at a first position of the body, the second roller is pivoted at a second position of the body, one end of the flexible element connects to the body, the third roller is pivoted besides the first roller in parallel and rotates with the first roller simultaneously, and a transmission element is used to surround axes of the first roller and the second roller; wherein, the rotating directions of the first roller, the second roller, the third roller and the transmission element are the same. The present disclosure provides another office machine using the same.