To advantageously perform fire resistant structure work for a through hole in terms of cost and efficiency by rationally remodeling a sleeve embedded for forming the through hole for a pipe in a pipe-expected position of a concrete structure.

The sleeve 3 is embedded for forming the through hole 2 for the pipe in the pipe-expected position of the concrete structure 1, and is manufactured from a thermally expansive heat resistant resin for substantially blocking up the pipe-inserted through hole 2 by the thermal expansion. The sleeve 3 forms a blocking-up part 3A for blocking up or almost blocking up clearance S formed between an inner peripheral surface and an outer peripheral surface of the pipe in a pipe axis X directional specific position by contacting with or approaching the outer peripheral surface of the pipe P inserted into the through hole 2.