To provide a boiler device having a heat transfer pipe structure which will not be damaged for a long period of time by effectively suppressing generation of stress in a protector weld part.

In the boiler device, suspended heat transfer units composed by arranging plural suspended heat transfer pipes 4 welded with protectors 11 for pipe contact wear prevention on outer circumferential faces in parallel with each other, and maintaining gaps between suspended heat transfer pipes by interposition of the protectors 11, are installed in a flow 3 of combustion gas. It is characterized by that a slit 13 is formed in the protector 11.