PURPOSE: To freely adjust the length of joints of foundation blocks by a method in which a foundation block with exposed nuts provided to buried reinforcing bars is adjacently set on the side end face or the bottom face of a dent, and the nuts are connected with long threaded bars.

CONSTITUTION: A rectangular block 1a is set on a leveling concrete SC, and long threaded bars 8 with male screws 8a and 8b are screwed with nuts 5a and 7a exposed from the side face 2a and a dent 3a, extensionally provided from the reinforcing bars 6a of the block 1a. Rectangular block 1b is set in the face of side end faces 2a and 2b at an interval of the joint length L slightly shorter than the whole length of the bar 8, and the bar 8 is connected with nuts 5b and 7b while being centered and turned to connected the blocks 1a and 1b. Ready-mixed concrete is packed into the joint portion S. The strength of the joint can thus be increased.