A jet engine comprising: a cylindrical casing; a main nozzle which is inserted in the casing so that a portion of the main nozzle protrudes from a trailing edge of the casing, an inside of the main nozzle being configured as a first flow path through which a jet flow flows, a space between the main nozzle and the casing being configured as a second flow path through which a bypass flow flows; a combustor which is provided inside the casing; and a noise reduction system which is provided in an exhaust side of the main nozzle, characterised in that: the noise reduction system includes: a chamber provided on an outer periphery of the main nozzle; and a plurality of microjet nozzles provided, in a downstream side of the chamber, at an exhaust side peripheral edge of the main nozzle; the chamber includes: a cylindrical inner peripheral wall which is configured as a portion of an outer periphery of the main nozzle; and a cylindrical outer peripheral wall which is configured as a portion of an outer periphery of the main nozzle and is formed so as to cover the inner peripheral wall; a supply path starting from upstream of the combustor passing through a space formed between the inner and outer peripheral walls of the chamber, and leading to the plurality of microjet nozzles is provided; the supply path is configured as a third flow path in which part of compressed air is supplied into the chamber from the first flow path positioned upstream of the combustor, is taken in the space formed between the inner and outer peripheral walls of the chamber, and further is led to the plurality of microjet nozzles; the plurality of microjet nozzles is configured to inject the compressed air, which has been supplied to the chamber, into the jet flow exhausted from the main nozzle, the jet flow being formed of combustion gas exhausted from the combustor; and in the supply path, the part of the compressed air is led to the plurality of microjet nozzles through a space formed between the inner periphery and the outer periphery of the main nozzle, and the space formed between the inner and outer peripheral walls of the chamber, without passing through a pipe. a cylindrical casing; a main nozzle which is inserted in the casing so that a portion of the main nozzle protrudes from a trailing edge of the casing, an inside of the main nozzle being configured as a first flow path through which a jet flow flows, a space between the main nozzle and the casing being configured as a second flow path through which a bypass flow flows; a combustor which is provided inside the casing; and a noise reduction system which is provided in an exhaust side of the main nozzle, the noise reduction system includes: a chamber provided on an outer periphery of the main nozzle; and a plurality of microjet nozzles provided, in a downstream side of the chamber, at an exhaust side peripheral edge of the main nozzle; the chamber includes: a cylindrical inner peripheral wall which is configured as a portion of an outer periphery of the main nozzle; and a cylindrical outer peripheral wall which is configured as a portion of an outer periphery of the main nozzle and is formed so as to cover the inner peripheral wall; a supply path starting from upstream of the combustor passing through a space formed between the inner and outer peripheral walls of the chamber, and leading to the plurality of microjet nozzles is provided; the supply path is configured as a third flow path in which part of compressed air is supplied into the chamber from the first flow path positioned upstream of the combustor, is taken in the space formed between the inner and outer peripheral walls of the chamber, and further is led to the plurality of microjet nozzles; the plurality of microjet nozzles is configured to inject the compressed air, which has been supplied to the chamber, into the jet flow exhausted from the main nozzle, the jet flow being formed of combustion gas exhausted from the combustor; and in the supply path, the part of the compressed air is led to the plurality of microjet nozzles through a space formed between the inner periphery and the outer periphery of the main nozzle, and the space formed between the inner and outer peripheral walls of the chamber, without passing through a pipe.