A gear position detecting apparatus (10) includes three magnets (15) fixed to a transmission housing (12a) for generating magnetism and three hole elements (16) fixed to the transmission housing for detecting magnetism generated from the magnets. A magnetism shielding plate (11) is provided between the magnets and the hole elements. The magnetism shielding plate is slidably and rotatably movable according to a shift pattern of a shift lever (5) and has a plurality of holes and a cut-out portion. The magnetism generated from the magnets is permitted or forbidden to pass through these holes or the cut-out portion according to the movement (2) of the magnetism shielding plate (11) which is moved by the shift lever. The hole elements output an ON-signal when the magnetism is permitted to pass through and an OFF-signal when the magnetism is forbidden to pass through. As a result, a plurality of combinations of binary signals are produced corresponding to gear positions.