A second seal material is coated on an annular seal surface constituted by a partition wall of a connector housing and a three-sided outer peripheral surface of a cover, and is joined with an annular base outer peripheral surface on the base, and the cover and the base are integrated with fastening screws at the four corners, and hold the three sides of a circuit board therebetween. Fastening surfaces of the base are embossed with a first depth so that bending strength is reinforced whereby a stable seal gap is generated, and corner outer walls and a connection outer wall are disposed at four corners and one side of the cover, so as to generate a retention gap to prevent outflow of the second seal material.