Abstract: A sensor device includes a mounting frame having open front and rear ends, and right and left inner side walls opposite to each other in a longitudinal direction and extending between the front and rear ends so as to define a passage. The mounting frame is adapted to be mounted such that the body of a user of the sanitary apparatus will be sighted by the passage. A sensor body is inserted into the passage, and has a front side proximate to the front end to emit and receive a light signal, and right and left lateral walls that face respectively and spacedly the right and left inner side walls. A pair. of pivotally mounting members are respectively disposed between the right lateral and inner side walls, and between the left lateral and inner side walls such that the pivotally mounting members effect pivotal mountings which are pivotable between angular positions about an axis parallel to the longitudinal direction.