The invention relates to a waterproof electronic control device such that a connector unit is inserted into at least one wall face of a case, a control substrate is incorporated in a housing chamber formed of the case and connector unit, an aperture portion and an upper face of the connector unit are covered with a cover, and a waterproofing member is disposed on a contact surface of each of the case, connector unit, and cover. A structure is such that a first inclined portion is provided in a side wall of one portion of the case, a regulating wall is provided in a direction opposing an inclined face of the first inclined portion, a second inclined portion of the connector unit is provided in a position opposing the first inclined portion and comes into contact with an inner face of the regulating wall when inserted into the case, and the first inclined portion and the second inclined portion come into contact at a final insertion stage of the second inclined portion.