To form a floor or a wall excellent in design effect making a tongue for connection inconspicuous by bonding veneer to the surface of a base material to color the same and coating the colored veneer with transparent paint and applying coloration to the connection part of a decorative panel.

Male tongues 2 are continuously formed to the end edges of a decorative panel material in the longitudinal and lateral directions thereof on one side of the panel material and female tongues are continuously formed to the end edges of the decorative panel material in the longitudinal and lateral directions on the other side thereof. The decorative panel material 1 is formed by bonding fancy veneer overlaid plywood 6 composed of veneer to the surface of a base material 5 composed of plywood and successively applying a colorant 7, a sealer 8 and transparent paint 9 to the surface to the fancy veneer overlaid plywood to apply surface decoration. The coloring agent 7 applied to the surface of the fancy veneer overlaid plywood 6 is applied to the parts positioned on the upper side of the male tongues 2 and plough grooves in all of the side surfaces of the decorative panel material and further applied to the upper surfaces of the male tongues 2.