A plate product for finishing a floor or wall is disclosed. The plate product includes a natural-stone surface plate which has a predetermined thickness and is cut to have a predetermined length and width. A reinforcing plate is cut to have a length and width corresponding to those of the natural-stone surface plate and attached to the lower surface of the surface plate. A base plate is cut to have a length and width which are larger than those of the natural-stone surface plate and attached to the lower surface of the reinforcing plate. The upper layer part of the base plate having a predetermined thickness is pushed horizontally at one lengthwise side surface and one widthwise end surface, and the lower layer part having a remaining thickness is pushed horizontally at the other lengthwise side surface and the other widthwise end surface.