PURPOSE: To improve the water resistance, grinding performance, and lapping performance of the captioned grindstone by using the combination of PVA, aldehyde, and acid, as the phenol-resin containing immersion liquid for a porous grindstone which is fixedly molded, thus improving the affinity with a PVA bond grindstone.

CONSTITUTION: A proper kind of PVA is used for grindstone bonding agent, and 5W95parts PVA by weight is used for 100parts phenol-resin by weight. Aldehyde group is necessary in 20W80pts.wt. with respect to 100parts. PVA by weitht. Acidic catalyst is hydrochloric acid, sulfuric acid, etc., and 5W10pts.wt. is required for 100parts PVA by weight. The grindstone is immersed into said immersion liquid and then dried, and heat-treated at 40W130°C for formal reaction and phenol-resin condensation, and further heat-treated at 130W200°C for several hours for hardening. Thus, the grindstone which is uniform and free from irregularity can be prepared without forming crack during heating. Moreover, a grindstone having the superior water resistance, strength, grinding performance, abrasion proofness, and the good lapping performance can be obtained.