PURPOSE: To provide a muffler which is constituted to reduce the generation of noise and generate a comfortable tone color free from dominant noise, even in a blower to generate loud noise.

CONSTITUTION: A sound absorbing material 7 formed of porous synthetic resin having a vent passage 6 communicated with an opening part and formed in a central part is contained in a cylindrical case 5, provided at two ends with side plates 4A and 4B each having the opening part 3, in such a state to be held by a protection frame 8 formed of a wire-netting. Further, a thin-walled vent pipe 20A having a diameter d1 lower than the diameter D of a ventilation trunk 6 and having length shorter than the length 10 of the ventilation trunk and having length 11 determined based on the wavelength of the acoustic wave of dominant noise of a blower is incorporated in the ventilation trunk approximately in the same direction as each other to constitute a muffler.