A communication apparatus mounted on a vehicle includes: a camera that captures a still image used for generating a map; a positioning circuit that positions a captured position of the still image; a control circuit that associates position information indicating the captured position with image data of the still image; and a communication circuit that establishes a radio communication with a roadside unit and transmits the image data by radio to the roadside unit, in which the control circuit rearranges an transmission order of the image data to be transmitted by radio to the roadside unit, based on the position information.