PURPOSE: To connect members to each other easily by fitting dovetail grooves arranged on the joint surfaces of the concrete members, on each other to form a vertical groove, and by filling up a vertical groove internal-space with concrete, after a vertical reinforcement is inserted into the vertical groove internal- space.

CONSTITUTION: Dovetail grooves 2 formed respectively on the joint surfaces 1a of a pair of concrete members 1 to be jointed to each other are fitted to each other, and the vertical groove space 5 of a butterfly cross-sectional-area is formed. Besides, vertical reinforcements 3 are arranged in parallel with each other, and a plurality of horizontal reinforcements 4 arranged at specified intervals are connected to the vertical reinforcements 3, and a reinforcement 7 fixed with binding wires or the like is formed. Then, the reinforcement 7 is inserted into the vertical groove space 5, and after that, the space 5 is filled up with concrete 6 to be hardened, and the members 1 are integrally bonded.