A coaxial cable A12 of a receiving antenna A1, a resin plate A13, and a connecting unit cover A15 are fused by thermal treatment, so that a gap between the outer coating of the coaxial cable A12 and the connecting unit cover A15, and a gap between the resin plate A13 and the connecting unit cover A15 are eliminated, whereby they are integrally configured. An antenna of the antenna unit, a coaxial cable, and a connecting unit cover are fused for coverage, and thereby it becomes possible to improve drip-proofness of the antenna unit by preventing water from entering from the gap between these materials when disinfectant is sprayed by misting, for example.