A movable body monitoring apparatus is mounted on a movable body and to receive movement data related to movements of other movable bodies. The apparatus includes an acquiring unit, a generator, a determining unit, and a monitoring unit. The acquiring unit acquires the movement data on the other movable bodies. The generator generates group information on a plurality of low-speed movable bodies which are determined based on actual speeds or types of the other movable bodies. The determining unit determines whether to generate the group information by the generator, in accordance with a travel environment. The monitoring unit collectively monitors movements of the plurality of low-speed movable bodies using the group information, when the group information is generated. The monitoring unit individually monitors the movements of the plurality of low-speed movable bodies, when the group information is not generated.