The apparatus 50 comprises a flange 52 which is fastened to a housing 12, a cable clamp 54 which has a first through hole through which the cable 14 is passed and which is arranged between the housing 12 and the flange 52, and an elastic member 56 which has a second through hole through which the cable 14 is passed and which is arranged between the housing 12 and the cable clamp 54. The flange 2 has a cable hole 66 which opens at an outer peripheral edge of the flange 52 and holds the cable 14. The elastic member 56 is sandwiched between the cable clamp 54 and the housing 12 when the flange 52 is fastened to the housing 12, elastically deforms, holds the cable 14 at the inside of the second through hole, and seals the cable lead-out hole 66.