To simply manufacture a plurality of floor materials, each of which is constituted so that the outer periphery of a core material made of a woody board is surrounded by a frame material made of plywood, at once to enhance productivity.

A large-sized substrate 6 is formed of a frame body 4, which is constituted by assembling a pair of front and rear frame materials 1 made of plywood and a pair of left and right frame materials 2 made of plywood into a rectangular shape and constructing one or a plurality of intermediate frame materials 3 made of plywood between the left and right frame materials 2 in parallel to these left and right frame materials 2, and the core materials 5 made of the woody board which are provided in the frame body 4 have the same thickness as the frame materials 1, 2 and 3 and of which the outer peripheries are formed of a raw material comprising the woody small pieces or woody fibers bonded to the respective frame materials 1, 2 and 3. This large-sized substrate 6 is cut in the direction parallel to the longitudinal direction of the frame materials 3 at the positions 1/2 the width of the arbitrary frame materials 3 to form a plurality of the floor materials 7.