To provide a front door slave set casing structure, with which a receiving voice quality is easily stabilized.

A camera cover 2 for protecting a camera is provided on the front face of a casing 1 of a front door slave set 10 with camera equipped with a camera 4, a hole 22 for microphone of a microphone 3 for introducing voices is opened on the camera cover, a holder 21 is provided for holding the microphone and the camera cover and the holder of the microphone are integrally molded. Thus, since the structure of an adhesive part is simplified and the microphone can be located proximately to the camera cover, the satisfactory receiving voice quality can be stably provided.