This pharmaceutical injection device may be provided with a main body case, a pharmaceutical syringe mounting portion, a piston, a piston feed screw or the like, and a cover. At a first end, the main body case may have an injection needle mounting portion to which an injection needle is mounted. The pharmaceutical syringe mounting portion may be provided inside the main body case, and a pharmaceutical syringe may be mounted thereto. The piston may be provided movably with respect to the pharmaceutical syringe that is mounted to the pharmaceutical syringe mounting portion. The piston feed screw or the like drives the piston. The cover may be provided on the first end side of the main body case and operates to open and close the injection needle mounting portion.