In an electronic control unit, a chassis is provided with a plate portion, and a circuit board is secured to a board-side attaching surface of the plate portion with a predetermined space secured relative to the plate portion. The chassis is further provided with a side wall protruding from the circumferential portion of the other surface of the plate portion and is mounted on a surface of a housing incorporating a device therein, with an end surface of the side wall being seated on the surface of the housing. A bus bar is fixed at a fixing portion thereof to the board-side attaching surface between the plate portion and the circuit board and is connected to a terminal of the device which is taken out from the housing. The bus bar is provided at plural free ends thereof with branch portions at which lead portions extend to be joined at end portions thereof to the circuit board. Elastic portions for reducing stresses which are developed at juncture portions of the lead portions to the circuit board as the temperature changes are formed between the base portion and the branch portions alongside the board-side attaching surface.