A circuit board (3) of an electronic control device has a connector fixing screw penetration hole (16) which a connector fixing screw penetrates, a resist layer (13) and a joining portion (23) which is formed at a circumference of connector fixing screw penetration hole (16) and to which the connector fixing screw can be soldered. Joining portion (23) is formed at an inner side of a resist layer opening (22) which is open at the circumference of connector fixing screw penetration hole (16). Joining portion (23) is formed so that an area of joining portion (23) located at an inner side of circuit board (3) with respect to a center (C1) of connector fixing screw penetration hole (16) is larger than an area of joining portion (23) located at an outer side of circuit board (3) with respect to the center (C1) of connector fixing screw penetration hole (16).