To reduce noise by intake sound generated when a blower sucks air without troubling inflow of air.

In this boiler comprising a combustion chamber to generate combustion of flames, a fuel supply passage to feed fuel into the combustion chamber, and a blower to feed combustion air into the combustion chamber in which intake sound is generated by an air current at an air intake port of the blower, an intake sound reducing duct is provided on the upstream side of an air current at the air intake port of the blower, the intake sound reducing duct comprises an intake sound reducing duct 6 having a duct outlet opening part 10 as an outlet for air from the duct, and a duct inlet opening part 11 as an inlet for air into the duct, the air intake port of the blower is connected to the duct outlet opening part 10, and for the intake sound reducing duct 6, it is set as (a duct inlet opening part surface)>(an intake sound reducing duct flow passage cross sectional area)>(a duct outlet opening part area).