To dispense with preparation of exclusive valley tiles shaped according to the roof gradient to be constructed, which reduces the stock of valley tiles.

This clay tile roofing method uses valley tiles of a size corresponding to a predetermined reference roof gradient 0.4 to form a valley inclining from the ridge toward the eaves in a tiled roof in which the roof gradient x to be constructed is set within a range of 0.40-0.60, wherein a preset pitch Px between stiffeners is selected corresponding to the roof gradient x to be constructed. A predetermined valley width can thereby be held substantially even when the roof gradient x differs from the predetermined reference roof gradient 0.4.