To provide a method of forming a fireproof structure without preparing a fireproof material even when there is some time until a penetration part is filled with the fireproof material after formation thereof.

In the method of forming the fireproof structure, the fireproof material 11 formed like a sheet is wound and stored in the penetration part K, an opening on both axial sides of the penetration part K is closed with the lid 22, and the fireproof material 11 is stored in the penetration part K. A lid 22 is taken out of the penetration part K to open the opening of the penetration part K, and the fireproof material 11 is removed from the penetration part K. Wiring and piping material are penetrated into the penetration part K, and the removed fireproof material 11 is filled into a gap between the inside of the penetration part K and outside of the wiring and piping material.