A cogeneration system includes an intake pipe having one end which communicates with the outside air and having the other end which is connected to an engine; a mixer disposed in the intake pipe to supply gas into the intake pipe; and an intake compressor for compressing a mixed gas which is a mixture of the air and the gas, wherein the intake compressor includes: a motor disposed in the intake pipe; and a compressor impeller which is disposed in the intake pipe, and rotates by the motor to compress the mixed gas.