An ECU 1 includes a circuit board 10, a connector 20 fixed to the circuit board 10 and a resin portion 50 covering the circuit board 10 and the connector 20. The connector 20 includes a housing body 22 and a cut-off receiving portion 27 projecting from the housing body 22. The cut-off receiving portion 27 includes a flange portion 28 projecting outward from the housing body 22 and a flexible wall 29 extending from the flange portion 28 and inclined to be closer to the housing body 22 toward a tip, and a part of the flexible wall 29 is embedded in the resin portion 50.