A manure spreader (1) includes a transport device (3) that transports manure loaded in a cargo box (2), a spreading unit (4) that spreads the transported manure over a farm field by causing beaters (40) rotatably supported by a frame (5) to rotate, and a horizontal drive shaft (61) that causes the beaters (40) of the spreading unit (4) to rotate, and the drive shaft (61) is located at the upper end portion of the frame (5) and the frame (5) is made to pivot about the drive shaft (61), so as to open the rear end portion of the cargo box (2). To open the frame (5), the frame (5) is first shifted backward by the pressing force of the manure, and the transport rate of the manure is controlled by detecting the backward shift of the frame (5), and then a hydraulic cylinder (87) is extended so as to release the frame (5).