The present invention comprises: an image acquisition unit 31 which acquires captured image data from a rear camera 2 that images an area rearward of a vehicle; a frequency detection unit 32 which detects the frequency of movement of the driver of the vehicle for changing the field of view from a rearview monitor 3 installed forward of the driver of the vehicle; a display image data generation unit 33 which generates display image data such that the captured image data acquired by the image acquisition unit 31 is cropped to include a greater range the higher the frequency detected by the frequency detection unit 32; and a display control unit 34 which displays, on the rearview monitor 3 installed forward of the driver of the vehicle, the display image data generated by the display image data generation unit 33.