To provide a floor structure with high heat insulating performance by eliminating heat insulation loss among strut materials in a lower section of a partition wall, that of a sill and that of an edge floor joist.

In this floor structure 1, a sub-floor material 4, which is composed of a thermoplastic foamed resin, is spread in a close contact state all over the top surface of a slab 3, and a finishing plate 7 is spread all over the top surface of the sub-floor material 4, so that a double floor can be formed. The edge joist 9, partition wall 2 or sill 20 of the double floor is installed on the top surface of the slab 3 via heat insulating boards 12, 18 and 21.

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