PURPOSE: To prepare the titled adhesive readily dissolving an acidic substance added thereafter, by the addition of PVC in the reaction of a phenol with formaldehyde in the presence of an alkali catalyst.

CONSTITUTION: In the preparation of a water-soluble resol-type phenol resin adhesive by the reaction of a phenol with formaldehyde in the presence of an alkali catalyst such as NaOH, PVC is added during or after the reaction and then an acidic substance such as phosphoric acid or ammonium chloride is added. Addition of the PVC renders said substance easily soluble, so that a particle board prepd. by use of the adhesive is difficultly swelled in the direction of thickness and forms no brown stain on the surface when wetted with water.