Provided is a boiler support structure able to greatly reduce the effect of seismic force thereon and able to vibrate integrally during an earthquake. The boiler support structure is provided with a main boiler body (3), a plurality of pillars (11a) standing over pillar legs (11b) on a foundation (1), a plurality of beams (11c) for connecting adjacent pillars (11a), a support steel frame (11) for supporting the main boiler body (3) in a suspended state, and seismic isolation devices (5) for supporting each of the plurality of pillars (11a). The seismic isolation characteristics of the seismic isolation devices (5) in the boiler support structure (10) are set in accordance with the horizontal reaction forces occurring in the plurality of pillar legs (11b).