A housing for an electronic control unit is constructed of an upper housing part (10) having a bottom opening and a bottom plate (20) which closes the bottom opening. The upper casing part is formed such that a plurality of said upper housing parts can be easily stacked on one another, with the upper housing parts then an automatic vacuum suction device can be removed, for example by one through. The side walls of the upper housing parts, which are opposed to each other are chamfered to extend and an edge portion (13) is formed at the bottom end of each inclined side wall. A U-shaped portion is formed at the peripheral portion to prevent the upper housing part is stuck in another upper housing portion when a plurality of upper housing parts is stacked vertically.