A vehicle controller with improved usability related to updating of a control program is provided. The vehicle controller is capable of updating a stored control program, based on update contents provided by a writing device. The control program includes a control code, and control data that is referred to when the control code is executed. The vehicle controller includes a nonvolatile memory that allows a first memory area and a second memory area to be switched and used alternately, the first memory area and the second memory area each storing both the control code and the control data, and an updating request determining unit that determines whether an updating request from the writing device requests updating of both the control code and the control data or requests updating of the control data only. When determining that updating of the control data only is requested, the updating request determining unit writes received control data to any given memory area in which a currently active control program is stored.