An object of the present invention is to provide an electronic control unit that curbs overflow of a sealant at a three-way junction of the sealant in the vicinity of a connector. The electronic control unit includes a first seal part 51 that seals between a base member 40 and a cover member 30, a second seal part 52 that seals between the base member 40 and a connector housing 20, and a third seal part 53 that is connected to the first seal part 51 and the second seal part 52 and seals between the cover member 30 and the connector housing 20. In a part (three-way junction) where the first seal part 51, the second seal part 52, and the third seal part 53 intersect, a space part 41JA1 that is connected to the recessed part 41 and recessed further from a surface forming the recessed part 41 is formed.