To provide a joining structure for a precast member of excellent durability, can join the fellow precast members with a high proof-stress.

This joining structure joins fellow precast floor plates 1, 1 arranged with a clearance 13. A perforated steel plate 3 with one part embedded in an inside is projected to arrange at least one hole 31 in the clearance, in joining side end parts 11 of both precast floor plates, the holes 31 of the perforated steel plate 3 projected from both precast floor plates are made substantially consistent in view from a direction right-angled to a face, in the clearance, a fill is filled into the clearance, and a prestress is introduced into a filled part 35 with the fill by an unbonded PC steel wire 33 inserted through the holes.