PURPOSE: To provide a bass reflex type active silencer without enlarging a device while ensuring desired output performance.

CONSTITUTION: An active type silencer comprises a cylindrical member 30, which has a large inner diameter larger than the external diameter of an exhaust tube 3, and which is provided with a gap AG in relation to the outer periphery of the exhaust tube, a sound wave output device 5, which is provided around the cylindrical member, and which has an annular vibration member 51 supported so that it is vibrated in the axial direction, and a housing 40, by which a sound wave output device is surrounded while opened in the direction of outputting sound wave, and with which a surrounding chamber ER is formed on the rear surface side of the vibration member 51 while forming an opening chamber OR on the surface side of the vibration member. The opening chamber and the surrounding chamber are communicated with one another through the gap Ag, to form a bass reflex structure. Sound is erased by having the sound wave of reverse phase interfered with the exhaust noise from the exhaust tube of an internal combustion engine.