An apparatus comprising: an action plan candidate generator configured to generate a plurality of action plan candidates based on a status of surroundings; an action plan candidate evaluator configured to assign an evaluation result to each of the plurality of action plan candidates; and an action plan determiner configured to determine an action plan based on the plurality of action plan candidates and the evaluation results thereof; wherein the action plan determiner includes: a selector configured to select one of the plurality of action plan candidates based on the evaluation results thereof; a merger configured to merge the plurality of action plan candidates based on the evaluation results thereof; a valid action plan candidate determiner configured to determine, from among the plurality of action plan candidates, one or more valid action plan candidates satisfying a predetermined condition; J and a divergence degree determiner configured to calculate J a degree of divergence between the one or more valid action plan candidates from among the plurality of action plan candidates and, in accordance with the degree of divergence, determine whether one of the one or more valid action plan candidates is to be selected on the basis of the evaluation results thereof by the selector, or the one or more valid action plan candidates are to be merged on the basis of the evaluation values thereof, in order to determine the action plan; characterized in that the valid action plan candidate determiner is configured to determine, as a valid action plan candidate satisfying the predetermined condition, an action plan candidate for which a predetermined time period has elapsed after the generation of the action plan candidate was started by the action plan candidate generator. an action plan candidate generator configured to generate a plurality of action plan candidates based on a status of surroundings; an action plan candidate evaluator configured to assign an evaluation result to each of the plurality of action plan candidates; and an action plan determiner configured to determine an action plan based on the plurality of action plan candidates and the evaluation results thereof; wherein the action plan determiner includes: a selector configured to select one of the plurality of action plan candidates based on the evaluation results thereof; a merger configured to merge the plurality of action plan candidates based on the evaluation results thereof; a valid action plan candidate determiner configured to determine, from among the plurality of action plan candidates, one or more valid action plan candidates satisfying a predetermined condition; J and a divergence degree determiner configured to calculate J a degree of divergence between the one or more valid action plan candidates from among the plurality of action plan candidates and, in accordance with the degree of divergence, determine whether one of the one or more valid action plan candidates is to be selected on the basis of the evaluation results thereof by the selector, or the one or more valid action plan candidates are to be merged on the basis of the evaluation values thereof, in order to determine the action plan; characterized in that the valid action plan candidate determiner is configured to determine, as a valid action plan candidate satisfying the predetermined condition, an action plan candidate for which a predetermined time period has elapsed after the generation of the action plan candidate was started by the action plan candidate generator. a selector configured to select one of the plurality of action plan candidates based on the evaluation results thereof; a merger configured to merge the plurality of action plan candidates based on the evaluation results thereof; a valid action plan candidate determiner configured to determine, from among the plurality of action plan candidates, one or more valid action plan candidates satisfying a predetermined condition; J and a divergence degree determiner configured to calculate J a degree of divergence between the one or more valid action plan candidates from among the plurality of action plan candidates and, in accordance with the degree of divergence, determine whether one of the one or more valid action plan candidates is to be selected on the basis of the evaluation results thereof by the selector, or the one or more valid action plan candidates are to be merged on the basis of the evaluation values thereof, in order to determine the action plan; characterized in that the valid action plan candidate determiner is configured to determine, as a valid action plan candidate satisfying the predetermined condition, an action plan candidate for which a predetermined time period has elapsed after the generation of the action plan candidate was started by the action plan candidate generator.