To prevent abrasion of a protector for a heat transfer tube of a fluidized bed combustion device to semi-permanently use the protector which is considered as a consumption article in a current one.

In the heat exchanger tube 20 provided with a straight tube part and a bent tube part inside of a fluidized bed wherein the flowing medium 1 flows and while the fuel burns, at least the outer surface of the bent tube part of the heat transfer tube 2 is covered with the protector 8, and a plurality of studs 10 for giving resistance to the fluid flowing outside of the protector 8 are provided, and a U-shape round steel 11 formed along the shape of the bent part of the heat transfer tube 2 is provided in both of a right and a left side surfaces of the protector 8.