The utility model discloses an accurately controlled fertilizer device. The device comprises a shell, wherein a cylindrical through hole is axially formed in the shell; a fertilizer inlet and a fertilizer discharge hole are formed in the upper end face and side face of the shell respectively; a screw is inserted in the cylindrical through hole; the outer diameter of the screw is matched with the inner diameter of the cylindrical through hole; one end of the screw is connected with a stepping motor; a left end cover and a right end cover are connected at the two axial ends of the shell respectively; the two ends of the screw are connected to the shaft holes of the left and right end covers respectively. The device has the beneficial effects that by arranging the screw matched with a hollow cylindrical cavity and connected with a relevant power device in the hollow cylindrical cavity and meanwhile forming the fertilizer inlet and the fertilizer discharge hole in the shell, fertilizers at the fertilizer inlet can be pushed to the fertilizer discharge hole along with rotation of the screw; as the thread spacing of the screw is constant, the discharged fertilizer quantity can become an accurate value and is not affected by the environment and the discharged fertilizer quantity in unit time can be adjusted via the rotating speed of the screw.