A silencer having improved noise reduction characteristics is disclosed. The silencer includes a first cylindrical connection pipe for guiding the flow of a fluid, a cylindrical expansion pipe communicating with the first connection pipe at one end thereof for guiding the flow of the fluid, the expansion pipe having a sectional area greater than that of the first connection pipe, and a second cylindrical connection pipe communicating with the other end of the expansion pipe for guiding the flow of the fluid. The expansion pipe has a length (L) decided depending upon a diameter (D) of the first connection pipe or the second connection pipe. According to the present invention, resonance caused by a pipe connected to the silencer is prevented, and therefore, the noise reduction efficiency of the silencer is improved.