To enable a fluidized sand transporting means to be arranged in flexible manner by an air transporting system, reduce an installing area and utilize air acting as transporting media also as cooling medium.

Fluidized sand S transported out of a fluidized bed furnace 1 is supplied to an air trasporting passage 18 through a sand receiving hopper 14. Fluidized sand S is transported with air acting as transporting medium supplied from a fluidized bed blower 10 in an air transporting passage 18. The fluidized sand S and rough materials K contained in the fluidized sand S are classified by a front stage cyclone 20. The classified fluidized sand S is circulated and returned back from an under-flow port 24 of a rear stage cyclone 21 into the fluidized bed furnace 1.