A medication administering device has mounted thereto a preparation syringe containing a preparation and comprises a substantially cylindrical syringe cover that supports the preparation syringe on the inner peripheral face side, a piston that presses on the rear end of the preparation syringe, and a piston case that surrounds the piston, that guides the outer peripheral face of the syringe cover in the direction of the piston on the substantially cylindrical inner peripheral face side, and that is mounted in a state in which the syringe cover is removable. The medication administering device comprises a syringe holder that guides the outer peripheral face of the preparation syringe in the direction of the piston on the cylindrical inner peripheral face side, and whose outer peripheral face is removably fitted together with the inner peripheral face of the syringe cover. A medication administering device comprises a syringe cover for mounting a preparation syringe to a main body, and has uneven faces of different angles of inclination on the end face of the syringe cover.