PURPOSE: To offer a boiler vibration isolating device which has an enhanced effect to reduce the seismic response load not only for a large earthquake but also for a medium or small one.

CONSTITUTION: A back stay 5 is attached to the outside of a boiler main body. Two or more elastoplastic elements are connected to a back stay 5 by inner binders 8 and outer binders 7 which located outside the inner binders 8. A steel beam 1a is held between the left and right side inner binders 8. The inner binders 8 are connected together by inner tie plates 10 and the outer binders 7 by outer tie plates 9a and 9b. A gap δt is provided between the outer and inner binders 7 and 8, so that the inner binders 8 act in a group during a medium or small earthquake and the outer binders 7 join the action during a large earthquake.