To provide a roof tile which enhances the cooling efficiency and snow-melting efficiency of a roof, and an air-conditioning supporting system which cools the roof and melts snow without mounting water sprinkling equipment on the roof, and does not impair the appearance of a building.

The roof tile 20 includes: a penetrating channel 23 which penetrates one end of the roof tile to the other end thereof; a diversion channel 24 which penetrates a surface of the roof tile from an intermediate portion of the penetrating channel; a tank 50 which is provided on the surface of the roof tile in such a manner as to cover an outlet of the diversion channel; moss 51 which is provided on the outer surface of the tank; and a water supply body 52 which is provided in the tank in such a manner as to penetrate it, and supplies water to the moss by making the water in the tank seep to the outside.