A housing structure for an in-vehicle electronic device is provided. A case body includes a top panel and a side wall continuously and integrally formed at a side edge of the top panel. The case body is configured to accommodate a control board therein. A plurality of brackets outwardly projects and extends from the side wall of the case body. The brackets are fixed to an attachment portion of a vehicle body. A plurality of reinforcement ribs are integrally formed between the brackets and the side wall of the case body at a position lower than the control board in a state where the case body is mounted on the vehicle body.