Onboard Update Apparatus and Update Processing Program

An onboard update apparatus includes a control unit that controls adoption of an update program by an onboard ECU installed in a vehicle, wherein the control unit attempts to communicate with an external server outside of the vehicle when a target onboard ECU for updating adopts the update program stored in a predetermined storage area in the vehicle; in a case where communication with the external server is successful, in a case where information relating to cancelation of the update program is acquired, adoption of the update program by the target onboard ECU for updating is canceled, and in a case where the information relating to cancelation cannot be acquired, the target onboard ECU for updating adopts the update program; and in a case where communication with the external server has failed, the target onboard ECU for updating adopts the update program.