The invention relates to a silencer which is convenient to assemble and excellent in silencing effect. The silencer comprises a shell unit and an inner shell unit, wherein the shell unit defines a shell space and is provided with a front-end air inlet for allowing airflow to enter along the first direction and a rear-end air exhaust; the inner shell unit comprises a first inner shell part which is provided with a through hole and has a first inner shell air chamber and a second inner shell part which is provided with the through hole and has a second inner shell air chamber; after flowing into the first inner shell air chamber from the air inlet, pressure air flows into the second inner shell air chamber by the deflection of an angle, and the pressure air can flow between the shell space and each inner shell air chamber and is exhausted from the air exhaust; and the air pressure generates a resonant sound wave in the first inner shell air chamber and also generates the other resonant sound wave in the shell space, the two resonant sound waves, after being mixed, interfere mutually to be attenuated and thus, the silencing effect is achieved.