The purpose of the present invention is to provide a coinjection device capable of using a syringe taking the orientation of the needle tip of the injection needle of the syringe or the inclination of the injection needle into consideration. The coinjection device (1) of the present invention is for executing the coinjection process of drawing up a drug from a container (10) using a syringe (11) and injecting same into another container (12). The device is capable of: detecting the respective widths of the projection images of the needle tip (11e) of the injection needle (11c) of the syringe when light is irradiated on the needle tip (11e) from multiple directions and detecting a first direction from the center of the injection needle (11c) in the radial direction of the injection needle (11) to the pointed end (11g) of the injection needle (11c) as the orientation of the needle tip (11e) according to the detected respective widths of the projection images and the respective light irradiation directions corresponding to said projection images.
