An injection device is provided with a stationary-side frame supporting a barrel, a movable-side frame rotatably supporting a screw, a pair of ball screws, and injection drive mechanisms includes servomotors configured to rotate the ball screws. A force detector such as a load cell and the like is disposed between the first ball screw and the movable-side frame. A dummy member is disposed between the second ball screw and the movable-side frame. A control unit controls the first injection drive mechanism based on the output of the force detector and controls the second injection drive mechanism based on the output of the force detector and an arithmetic operation performed in consideration of the respective spring constants of the force detector and the dummy member.