A medication administering device, to which a preparation syringe containing a preparation is mounted, and which administers a preparation to a living body, and comprises a main body; a cylindrical syringe holder that is provided to the main body and into which the preparation syringe is inserted from the rear end side; a cylindrical syringe cover that supports the preparation syringe on the inner peripheral face side, and into which the preparation syringe is inserted from the distal end side; an inner case that guides the syringe cover and is removably fitted together with the syringe cover; and a distal end cap that guides the main body and is removably fitted together with the main body, and moves in conjunction with the syringe cover during attachment to the main body.