PURPOSE: To make contact of a grinding wheel detectable so accurately and speedily, by installing a device, which speedily and accurately detects an interval between the lower end of a wheel outer circumference and the top of a working table, in a forming grinder performing one pass grinding on the wheel outer circumference.

CONSTITUTION: At the time of detecting a wheel position of a grinding machine, a wheel vertical shaft 2 is made to go up to an absolute zero position of a measuring machine 6. Next, this vertical shaft is made to go down in rapid traverse up to a set point from the absolute zero position of the measuring machine 6 in advance. And, a contact table 18 is made to go up by piezoelectric element 19 till contact between a grinding wheel 1 and this contact table is detected by an AE sensor 16. Afterward, the piezoelectric element 19 is stopped by a controller 10, and a read value out of the measuring machine 6 and a difference ±Δt in height between the contact table 18 when the numerical value of a digital-to-analog converter 21 is zero and a working table 7 are added to displacement of the piezoelectric element 19 proportioned to the numerical valve of this converter 21, whereby a wheel contact position is calculated.