An action plan is generated even when the own position is unknown in order to move autonomously. A route is planned for each position constituting an own-position candidate on the basis of status of surroundings. Multiple candidates of an action plan constituting multiple action candidates are generated on the basis of the planned routes. An evaluation value is set to each of the generated multiple action plan candidates. The action plan is determined using the action plan candidates in accordance with their evaluation values. This technology is applied advantageously to multi-legged robots, flying objects, and onboard systems each controlled by an onboard computer to move autonomously.