To improve the truing accuracy of a high hardeness honing grinding wheel which consists of a diamond grinding wheel, a CBN grinding wheel, or the like.

Center holes 15 and 16 are formed at both end faces of an expansion rod 9 which expands and contracts a honing grinding wheel 7 together with a grinding wheel shoe 6. After regulating to be in a specific expansion condition by using an adjust nut 29, the whole body of a honing head 1 is supported at both sides by the centers 32 and 33 of a cylindrical grinding board by using the center holes 15 and 16, so as to grind by a truing grinding wheel G. In the honing processing time, a push rod is connected to a female screw part 17, as well as the adjust nut 29 is removed.