PURPOSE: To obtain a position detecting device which is subminiature, high in resolution and accuracy, and of non-contact type.

CONSTITUTION: A movable plate-like ferroelectric body 1 is introduced in between an upper and a lower fixed plate-like ferroelectric body, 2 and 3, and a primary capacitor electrode plate 4 and a temperature compensating capacitor electrode plate 5 are provided onto the surfaces of the ferroelectric bodies 2 and 3. By this process, a position detecting device of this design can be lessened in size and enhanced in resolution making use of a relation between the travel and the dielectric capacity change of the movable plate-like ferroelectric body 1. Capacitors 4 and 5, the plate-like ferroelectric bodies 1 to 3, and cases 11 and 13 where these capacitors and ferroelectric bodies are housed are set very small in thermal expansion coefficient, and a differential system by the temperature compensating capacitor electrode plate 5 is adopted to prevent measurement errors from occurring due to temperature change. Furthermore, a liquid ferroelectric body is inserted between the movable plate- like ferroelectric body 1 and the upper and the lower fixed plate-like ferroelectric body, 2 and 3, to enable the position detecting device to be of non-contact type.