To provide a method and a device for measuring a clearance which can easily perform high accurate clearance measurement by performing comparison operation treating at a speed in accordance with a response speed of a displacement sensor without being limited by a processing speed of a software in a CPU of the clearance measuring device.

Calculation of a maximum/minimum values based on an output pulse front displacement sensors 62, 64 is successively performed by a physical step, the calculated maximum/minimum value is presented to a CPU 22, and it performs only clearance calculation based on the maximum/minimum value. Accordingly, without being influenced by a processing speed of a software of the CPU 22, a rich data from the displacement sensors 62, 64 is efficiently processed, so as to perform high accurate clearance measurement.