PURPOSE: To easily produce a panel material in which a facing is not peeled by folding one part of the facing to the rear side and forming anchor pieces at a plurality of parts of at least one side of facing.

CONSTITUTION: Anchor pieces 11 are formed in the proper parts of the respective facings 2. The anchor pieces 11 are formed by firstly forming the cruciform notches 12 in the prescribed parts of the facings 2 and then folding these notched parts to the rear side along an alternate long and short dash line by a folding machine, etc. These anchor pieces 11 are buried into the expandable material 5 and function as the anchors of the facings 2. The respective anchor pieces 11 are made independent from the adjacent anchor pieces 11 and a small chamber such as a honeycomb structure is not formed. Therefore flow of the expandable material is not interrupted and the expandable material 3 can be spread on the whole face of the facings 2. Further these anchor pieces 11 are preferably tilted for the facings 2 in order to enhance the function of the anchor.