PURPOSE: To foresee the impossibility of conversion due to lock being out of order and elongate a period of maintenance and inspection in a detector for lock being out of order of an electric point machine for shifting the turnout of a railway by detecting the shifting position of the turnout with high accuracy and transferring the data.

CONSTITUTION: Line sensors 5, 6 are normally irradiated by light emitting diodes 1, 2 independently for detecting a fixed position and opposite position sides to project a gap between movable slits 3, 4 mounted on a locking lever shifting together with a tongue rail onto line sensors 5, 6. The projecting condition is cyclically collected to a transmitting part. The fixed position is distinguished from the opposite position from the projecting position and width or presence of projection, or abnormalities in the apparatus including an oil stain are detected and then detailed positional data is digitally transferred to the outside.