A recognition unit recognizes a surrounding situation of a mobile unit. A determination unit determines whether the mobile unit is traveling in an acceleration section or a merging section of a merging lane when the mobile unit changes lanes from the merging lane to a receiving lane based on the recognized surrounding situation. A control unit, when it is determined that the mobile unit is traveling in the acceleration section, causes a notification device installed in the mobile unit to execute merging assistance related to acceleration, and when it is determined that the mobile unit is traveling in the merging section, causes the notification device to execute merging assistance for encouraging confirmation of a situation of the receiving lane, and suppresses the merging assistance related to acceleration as compared with a case where it is determined that the mobile unit is traveling in the acceleration section.