To provide the clay-tile roofing structure of plain tiles capable of being easily executed in the clay-tile roofing structure of the plain tiles in which the adjacent plain tiles in the horizontal direction are abutted and the ridge-side end sections of the plain tiles are used as lap allowance.

Engaging holes 4 opened to at least lower sections are formed to a rear 12 at the side end section of the plain tile 1 while a connecting material 2 combining a throating is interposed just under the abutting end sections of the plain tiles 1 adjacent in the horizontal direction, and projecting sections 3 formed to the connecting material 2 are fitted into the engaging holes 4.