A composite image generation unit of a CPU of a console combines a camera image obtained by capturing an image of a subject located in an irradiation field using a camera and a positioning index image indicating a set position of the subject, which has been set in advance with respect to an in-image cassette position that is the position of the electronic cassette in the camera image, to generate a composite image. In a case in which the in-image cassette position is changed with the movement of the electronic cassette, the composite image generation unit changes a display position of the positioning index image with the change in the in-image cassette position.