To provide a fireproof treatment tool and a fire resistant structure for a penetration part, which are capable of reducing a used amount of thermal expansion material to reduce manufacturing cost.

A fireproof treatment tool 11 includes a fireproof body 12 formed into a cylindrical shape through which a conduit tube P can be passed with thermal expansion material capable of keeping its shape by itself and inserted into a through hole Wa, and a filler 21 filled in between an outer face of the conduit tube P and an inner face of the fireproof body 12 and made of non-thermal expansion material. The filler 21 will be compressed in a case of fire by expansion of the fireproof body 12 due to heat of the fire so as to close a gap to be formed due to burning of the conduit tube P.