An object is to provide a technique capable of increasing waterproofness of an electronic unit. An electronic unit includes: a case including an opening; a circuit board housed in the case through the opening; and a cover attached to the opening, wherein a protruding portion is provided on at least one side wall of the case, and the protruding portion includes a step that causes an opening side portion of the side wall to protrude further outward relative to a rear side portion of the side wall, and is provided so as to extend along the periphery of the opening.