To make it possible to build a durable building at a low cost and in a short construction time period without skilled workers by inserting an end of one member to a recessed groove in another member and injecting a hardening filler to a gap in the recessed groove thereby connecting the members together.

A dovetail groove 12 is made in each pedestal at each end of upper and lower board-like horizontal members 1. The lower horizontal member 1 is fixed to a footing made of gravel 91 and leveling concrete 92. A projection 22 is inserted to each dovetail groove 12 of the horizontal member 1 in such a manner that each lower face of right and left vertical members will touch the upper face of an outer levee 16. Thereafter, a gap between the dovetail groove 12 and the projection 22 is filled up with a hardening filler 3. After the filler is hardened, the upper horizontal member 1 is placed on the right and left vertical members 2 so that the projections 22 of the right and left horizontal members 2 are inserted to the dovetail grooves 12, and each gap in the dovetail groove is filled up with the hardening filler 3. When the filler 3 is hardened, the construction of a box culvert can be completed.