Abstract: A multi-joint fish robot capable of rapid acceleration propulsion, including: a main body segmented into a first body, a second body and a third body; joints connecting the respective bodies; and a caudal fin provided at an end portion of a third body, and swims forming a curve by operations of the joints. The fish robot has a first occupancy ratio of a length of the caudal fin to a full length of the fish robot with respect to a swimming direction, in which the fish robot swims, and the first occupancy ratio ranges from 0.15 to 0.35, or the fish robot has a second occupancy ratio of a length of the first body to a length of the main body excluding the caudal fin with respect to a swimming direction, in which the fish robot swims, and the first occupancy ratio ranges from 0.45 to 0.75.