A drug injection device (100) comprises a main body case (1) having an injection needle let-in/let-out opening (5), a drug syringe mounting component (6) that is provided inside the main body case (1) and in which a drug syringe (7) is mounted, a piston (12) that is movable with respect to the drug syringe mounting component (6), a drive mechanism (14) that drives the piston, a controller (23) that is electrically connected to the drive mechanism (14), and an acceleration sensor (24) that is electrically connected to the controller (23). This drug injection device (100) allows the injection of a drug to be carried out safely and properly.
