The invention discloses a cooperatively-mounted paddy field flatting device. The paddy field flatting device comprises supporting mounting plates which are vertically arranged in a left-right symmetric manner, wherein telescopic deflection connecting structures are horizontally arranged at the front and rear ends of the supporting mounting plates in opposite directions and comprise a plurality ofrotating connecting rods, the rotating connecting rods are sequentially rotatably connected to the supporting mounting plates on two sides through rotating shafts, limiting rotating threaded holes arehorizontally formed in supporting mounting plates on the opposite sides of the rotating connecting rods at the left and right ends in a penetration manner, and limiting rotating screw columns are cooperatively arranged in the limiting rotating threaded holes; and movable supporting mounting frames are vertically arranged on the left side of the supporting mounting plate on the left side and the right side of the supporting mounting plate on the right side, and guiding mounting structures are horizontally arranged between the supporting mounting plates in an equal interval manner through the cooperation with the telescopic deflection connecting structures at the front and rear ends. The paddy field flatting device has the advantages of compact structural design, stability in guiding and mounting, strong adaptive capacity, good interchangeability, good multi-flatting effect and the like.