An embodiment of this invention discloses a folding mechanism of a rowing machine that comprises a first frame, a second frame, a saddle member, and a control member. A front of the second frame includes a guiding portion that comprises an operation cut and a storage cut. The saddle member fixes with a rear end of the first fame and straddles on the rear end of the first frame. The saddle member includes a slot, and the first frame pivotally connects with the second frame via a pivot of the saddle member. The control member is arranged below the first frame and includes a bar at its rear end. The rowing machine can be folded for storage or spread for operation by switching the bar into the storage cut or operation cut.