PURPOSE: To enable easy and accurate measurement without adding new control function for measurement by controlling a probe attached to a stone holder so that it is moved in contact with a tooth surface of a gear for tooth shape measurement from deflection of the probe.

CONSTITUTION: In a gear grinder with NC, a grinding wheel 9 formed in the shape of a tooth groove of a gear to be ground is supported by a stone holder 7, and the grinding wheel 9 is rotated and driven by a wheel spindle motor 8. Here, a probe 23 such as an electric micrometer is attached to the stone holder 7 through a holding arm 22. Also, stoppers 24 and 25 for defining the measurement position and the storage position of the holding arm 22, respectively, are provided at the stone holder 7. By this constitution, the probe 23 is moved along the contact point of a base circle in contact with a tooth surface of the gear, and the stone holder 7 and the gear are controlled at the same time. And the tooth shape of the gear is measured based on deflection of the probe 23.