To automate grinding wheel replacing work in a bearing inner surface grinder.

A wrench mechanism portion 11 attaching/detaching a grinding wheel 5 to/from a grinding wheel quill 4, and a grinding wheel loader mechanism portion 21 supplying/discharging the grinding wheel to/from the wrench mechanism portion are provided. A spindle table 1 moves to a grinding wheel attaching/detaching position after detecting wear of the grinding wheel, and moves forward toward the wrench mechanism portion. After fitting a hexagonal rod wrench 12 of the wrench mechanism portion in a hexagonal hole of a grinding wheel stopping screw 6, the spindle table 1 is moved backwardly while reversely rotating the hexagonal wrench to remove the grinding wheel stopping screw and the grinding wheel from the grinding wheel quill. A revolving loader 21 of the grinding wheel loader mechanism portion discharges the removed grinding wheel, and a new grinding wheel is supplied from a grinding wheel supplying rod 23 that is a stock portion to the wrench mechanism portion. While normally rotating the hexagonal rod wrench, the spindle table 1 is moved forward to attach the grinding wheel stopping screw and the grinding wheel to the grinding wheel quill.