An electronic circuit unit in which a mold exclusion part, having a rear surface side covered by mold resin and a front surface side exposed from an outer case, is provided at a part of a plate surface of a circuit board which is mounted with electronic components and is covered by the outer case formed by the mold resin. The outer case is multi-material molded using plural kinds of resin having different fluidities. A rear wall of the outer case located on the rear surface side of the mold exclusion part is made of one of the plural kinds of the resin having a fluidity higher than a fluidity of another one of the plural kinds of the resin constituting the other portion of the outer case.