PURPOSE: To reduce the amount of overflow of grout when precast members are connected.

CONSTITUTION: Precast members 1A, 1B are formed by embedding a joint 5 and a reinforcing bar 3 whose one end has been connected to the joint 5. When the precast members 1A and 1B are connected to each other, the projected part of the reinforcing bar 3 of the precast member 18 on one side is inserted into the housing hole 7a of the joint 5 of the precast member IA on the other side. In this state, grout 25 is filled through an injection hole 1a. The grout 25 is filled into the housing hole 7a and then discharged through a discharge hole 10a. Prior to filling of the grout 25, the opening end of the discharge hole 10a is closed with a plug 30. This plug 30 has a small vent hole 30a whose diameter is smaller than the discharge hole 10a. The grout 25 overflows slightly through this vent hole 30a. The filling of grout 25 inside the joint 5 is confirmed by th is overflow.