PURPOSE: To perform uniform filling of concrete by a method wherein outflow and inflow of concrete at a building material made of a steel as the core or the reinforcing bars of a concrete structure are promoted.

CONSTITUTION: In a building material 1 made of a steel formed in such a manner that a plate-form steel material 2 provided on both sides with coupling parts 4 for intercoupling building materials 1 made of a steel and an H-steel 3 are combined together, the plate-form steel materials 2 are joined with the outer surfaces of two flanges 5 of the H-steel 3 along the direction of length and eccentrically in the direction of the width of the flange 5. Concrete flow holes 7 are formed at intervals in the direction of the length of steel plate parts 6 in the steel plate parts 6 of the plate-form steel material 2 on the eccentric side.