The present invention not only improves the utilization of the rice transplanter and portable fertilizer spreader by utilizing the existing rice transplanter and portable fertilizer spreader, but also improves the efficiency of fertilizer spreading work by allowing continuous operation for a long time without frequent fertilizer replenishment during the fertilizer spreading process. The present invention relates to a fertilizer spreading device for a rice transplanter to be able to increase. Fertilizer spreading device for mounting rice transplanter according to the present invention, A support frame 10 which is coupled to the rice transplanter 200 from which the hair transplanting apparatus is removed, and a fixing piece 11 for coupling with the rice transplanter 200 at a rear lower end thereof； A storage tank 20 fixedly installed at the rear of the support frame 10 and provided with a cover 21 freely opened and closed at an upper end thereof, and an outlet 22 for an external outflow of fertilizer stored at a lower end thereof； Transfer screw 32 that is connected to the outlet 22 of the reservoir 20, which rotates in accordance with the rotation of the connecting shaft 33 which is connected to the drive shaft 220 of the rice transplanter 200 in the main pipe 31 in the main pipe (31). Is provided, the transfer line 30 is provided with a connection pipe 34 is freely bent at the top of the main pipe 31； The support frame 10 is installed at the lower front, and the rotating plate 42 for repeating the forward and reverse rotation in accordance with the rotation of the drive motor 41 is provided on the upper surface of the body (40 '), and is supported on the lower rear of the body (40') A cradle 40 provided with a connection column 43 inserted and fixed to the frame 10； Spreader body which is mounted on the upper surface of the rotating plate 42 of the cradle 40, the stopper 52 through which the end of the connecting pipe 34 of the transfer line 30 passes through the op
