A construction machine comprising: a lower traveling body; an upper turning body which has an engine room and an upper frame including a bottom plate formed with an opening hole communicating with an inside of the engine room, and which is turnably mounted on the lower traveling body; an engine accommodated in the engine room; an exhaust duct provided in the engine room, for guiding air having cooled the engine to the opening hole, to exhaust the air to the outside of the engine room; wherein the exhaust duct includes an intake port for taking in the air in the engine room and an exhaust port for exhausting the air taken in from the intake port toward the opening hole; and a projecting bracket which is a bracket for supporting the engine, characterized in that the projecting bracket includes an end portion on one side fixed to the upper frame inside the exhaust duct, and an end portion on the other side projecting to the outside of the exhaust duct, wherein the exhaust duct further includes an opening for causing the end portion on the other side of the projecting bracket to project to the outside of the exhaust duct, and wherein the projecting bracket includes: a pair of engine support legs formed by a pair of plate members stood at an interval therebetween, each of the engine support legs including a base end portion fixed to the upper frame in the exhaust duct, and a front end portion projecting to the outside of the exhaust duct by passing through the opening; an engine mount plate which is connected to the respective front end portions of the pair of engine support legs and allows the engine to be mounted on the engine mount plate; and a reinforcement plate arranged between the pair of engine support legs so as to close the opening of the exhaust duct, and connecting the pair of engine support legs to each other. a lower traveling body; an upper turning body which has an engine room and an upper frame including a bottom plate formed with an opening hole communicating with an inside of the engine room, and which is turnably mounted on the lower traveling body; an engine accommodated in the engine room; an exhaust duct provided in the engine room, for guiding air having cooled the engine to the opening hole, to exhaust the air to the outside of the engine room; wherein the exhaust duct includes an intake port for taking in the air in the engine room and an exhaust port for exhausting the air taken in from the intake port toward the opening hole; and a projecting bracket which is a bracket for supporting the engine, characterized in that the projecting bracket includes an end portion on one side fixed to the upper frame inside the exhaust duct, and an end portion on the other side projecting to the outside of the exhaust duct, wherein the exhaust duct further includes an opening for causing the end portion on the other side of the projecting bracket to project to the outside of the exhaust duct, and wherein the projecting bracket includes: a pair of engine support legs formed by a pair of plate members stood at an interval therebetween, each of the engine support legs including a base end portion fixed to the upper frame in the exhaust duct, and a front end portion projecting to the outside of the exhaust duct by passing through the opening; an engine mount plate which is connected to the respective front end portions of the pair of engine support legs and allows the engine to be mounted on the engine mount plate; and a reinforcement plate arranged between the pair of engine support legs so as to close the opening of the exhaust duct, and connecting the pair of engine support legs to each other. a pair of engine support legs formed by a pair of plate members stood at an interval therebetween, each of the engine support legs including a base end portion fixed to the upper frame in the exhaust duct, and a front end portion projecting to the outside of the exhaust duct by passing through the opening; an engine mount plate which is connected to the respective front end portions of the pair of engine support legs and allows the engine to be mounted on the engine mount plate; and a reinforcement plate arranged between the pair of engine support legs so as to close the opening of the exhaust duct, and connecting the pair of engine support legs to each other.