To eliminate the need for troublesome formworks and the bearing of an upper concrete member, to inject mortar at a time and to connect upper and lower concrete members firmly and accurately.

Sleeves 2 are buried to the lower section of a main body, and reinforcements 3 for connection, in which lower end sections are inserted into the sleeves 2, are buried vertically into the main body and the upper end sections of the reinforcements 3 for connection are projected from the top face of the main body. A required number of concrete members, in which the rececced sections 5 for connection of mortar 4 are formed to the top faces of the main bodies, are superposed vertically by inserting the reinforcements 3 for connection projected from the top faces of lower concrete members 6 into the sleeves 2 of upper concrete members 6A. Mortar 4 is injected from the filler holes 7 of the sleeves 2, and the insides of the sleeves 2 and the recessed sections 5 for connection are filled with mortar and the upper concrete members 6A and the lower concrete members 6B and the reinforcements 3 for joining these members are coupled.