To provide a sleeve for a concrete through-hole which is excellent in workability and which makes possible favorable finishing of a concrete structure.

The sleeve 10 is constituted by a sleeve body 12 and fixation retainers 40A, 40B. The sleeve body 12 consists of an inner cylinder 14 and an outer cylinder 22, both of which are engaged with each other so that they can slide axially. The fixation retainers 40A, 40B are engaged with the inner side at both ends of the sleeve body 12 with possible sliding and turning. Then, projections 18, 28 are provided on the end-part inner peripheral surfaces on the mold 60 side of the inner cylinder 14 and the outer cylinder 22, and a groove 50 which is engaged with the projections 18, 28 is formed on the side of the cylindrical part 42 of the fixation retainers 40A, 40B. After a nail 48 has been driven into the through-hole 46 of the inner rib of the fixation retainers 40A, 40B which then are attached on the mold inner surface 60A, the shortened sleeve body 12 is inserted to the space between reinforcing iron bars 62. Then concrete 64 is placed in the mold 60, and concrete is poured. Then, the mold 60 is removed after curing, and the fixation retainers 40A, 40B are removed from the sleeve body 12 while being rotated.