A separator plate is used to separate a cable from structural parts housed in a casing. The back surface side of the separator plate facing a structural part is provided with a concave portion to fit to the structural part. The front surface side of the separator plate facing a cover of the casing is provided with a groove for accommodating and routing the cable. The groove is formed by making a portion on the front surface side that avoids a protrusion on the surface side due to the concave portion provided on the back surface side protrude toward the cover of the casing.