To provide an environment-friendly outboard motor of a racing boat, which can be safely and promptly maintained.

An outboard motor 1 comprises in order from below: a lower unit 2; a motor unit 3 which is attachably/detachably mounted on the lower unit 2 from above; and a battery unit 4 which is attachably/detachably mounted on the motor unit 3 from above. A plurality of locking devices 15 are provided in a lower part of a peripheral side surface of a lid body 4A3 of the battery unit 4 and a lower part of a peripheral side surface of a box body 3A1 forming a box 3A of the motor unit 3. The battery unit 4 which is mounted on the motor unit 3 from above is attachably/detachably mounted and fixed via a packing 14 by means of the locking device 15.