PROBLEM TO BE SOLVED: To obtain the subject fertilizer applicator-mounting structure that can firmly fix the fertilizer applicator by mounting the fertilizer applicator to a specific position in the fertilizer applicator in which the application unit is supported on the transplanter side. SOLUTION: In the rice paddy working machine equipped with a fertilizer application unit for applying the fertilizer along the rice plant rows, the mounting seat 20 is formed on the planter case 19 and the fertilizer application tool is attached to the mounting seat 20. At this time, this mounting seat 20 is a mounting plate that has the front face wall 20a and the side face wall 20b and this mounting plate is preferably attached to the front face and the side face of the planter case 19. Thus, the mounting seat 20 can be firmly fixed from the two faces of the front and the side and thereby the fertilizer application tool can be firmly fixed.
