Plywood for wallpaper underlayment is manufactured using 100% domestic softwood plywood made from Japanese cedar and Japanese cypress as the base material. Knot holes and cracks, which are characteristic of softwood plywood, are repaired and smoothed through a special surface-filling treatment (putty repair), after which liner paper is applied to the surface. The product is used as a substrate material for walls and ceilings before wallpaper installation. The liner paper also helps prevent resin bleed-through and stains from the plywood, thereby reducing the risk of wallpaper discoloration. Other notable features include high screw holding strength, superior durability compared with competing products, and excellent workability during installation. When used as a wall substrate in residential and office buildings, it enables secure installation of heavy fixtures, improved durability, and a high-quality finished appearance.