To provide a firm and uniform on-site connection between reinforcements through the site construction work of reinforcing blocks.

The reinforcing block such as a reinforcing bar cage comprises reinforcement 11, a reinforcing frame 13 and reinforcing bars. A part or the whole of the reinforcement 11 of the block is caused to slide on the end of the opposite reinforcement 11 of an adjacent reinforcing block so that the amount of clearance between the ends of both reinforcements 11 is set at a predetermined size or the pressure of contact between both ends is held at a predetermined pressure. Thereafter, the reinforcements are welded together by induction heating or by gas pressure welding, or both reinforcements 11 are connected together by a mechanical connection using female screws or the like.