A gear detection switch apparatus may include a detection unit into which a magnetization target is inserted at a front part thereof, the detection unit having a printed circuit board (PCB), a front housing having an open front end and into which the detection unit is inserted so that a frontal end of the PCB is exposed through the open front end, a rear housing connected to a rear side of the front housing, wherein a connection boundary between the front and rear housings is molded with a molding material, a Hall sensor device coupled to the exposed frontal end of the PCB, and a finishing closure molded over the open front end of the front housing.