Eccentric-swinging device for a sanding machine

An eccentric-swinging device for a sanding device having a machine body mounted with a working platform at one end thereof, one lateral side of the working platform being a sanding module having a sanding belt, the sanding module having a support frame with two ends respectively mounted with a driving roller and a driven roller, the sanding belt surrounding the driving roller and the driven roller, wherein the driven roller with a shaft rod is mounted with an eccentric swinging device which provides an eccentrical movement, the eccentric-swinging device comprises a floating frame, a transmission structure and a flat plate mounted onto the machine body, a center section of the floating frame is provided with a shaft seat, and a bottom face of the support frame is mounted with corresponding bearings such that the shaft seat holds the bearings to form a rotating support for the floating frame, and in between the floating frame and the flat plate, a spring which can be pulled downward is mounted, and the transmission structure is located at the floating frame, corresponding to one lateral side of the flat plate, the transmission structure is synchronously driven by the shaft rod of the driven roller, and the flat plate is mounted with a rotatable shaft center, wherein a free end of the shaft center forms into an eccentric post, and a bearing urges the top face of the flat plate on the eccentric post, thereby the sanding belt produces a reciprocating sanding movement.