To provide box-culvert laying technique, by which laying construction works can be conducted efficiently and safely by using one carrier truck even when there are curved sections such as a sharp curve, a corner, etc., in the intermediate sections of a conveying passage.

A box-culvert carrier truck 21 can travel along two rails 14 installed on both sides of subgrades 13a, 13b, in which box culverts 12 are laid, and a turntable 15 for changing the progressive direction of the carrier truck 21 is mounted in the curved section 19 of the subgrades 13a, 13b. Accordingly, the carrier truck 21 can be reciprocated along the rails 14 between a box-culvert loading place 17 and a box-culvert loading predetermined place 18 through the turntable 15 at the curved section 19, and laying construction works are conducted by successively transporting and placing the box culverts 12 up to laying predetermined places by using the carrier truck 21.