A semiconductor device has a position estimation part calculating an estimated position of a mobile at a scheduled time to project a message image, based on movement information of the mobile, a reference image signal output part deciding a reference area being an area to project a reference image, based on a relative positional relation between the mobile at the estimated position and the projection area, and outputting a reference image signal being a signal of the reference image, a test image signal acquisition part acquiring a test image signal being a signal of an image obtained by imaging the reference area with the reference image projected thereon, and an image adjustment part adjusting the message image signal, based on the reference image signal and the test image signal.