To provide a floor structure and a floor panel of a building which make it possible to shorten a term of work, to make a structural skeleton small in size and to facilitate work for fitting with no need of specific skill.

A deck plate 4 being provided on a floor beam 1, a gypsum- series board 5 and plywood 6 are provided in a laminated state on the deck plate 4 and floor finish is made for the upper surface of the laminate. In execution of this work, a floor panel 2 constructed by joining and integrating the deck plate 4 and the board and the like 5 and 6 is used and this floor panel 2 is fitted to the floor beam 1, joined thereto by bolts 11.