A construction machine, comprising: an engine room; a floor constituting a bottom surface of the engine room; an engine provided in the engine room such that a ventilation gap is formed below the engine; a hydraulic pump provided in the engine room on an exhaust side serving as one side of the engine in a left-right direction; a fan which is provided in the engine room on an intake side serving as an opposite side of the engine to the hydraulic pump, and which, when the fan is rotated, generates a cooling airflow that includes a lower airflow passing through the ventilation gap and flows from the intake side to the exhaust side; and an exhaust duct formed of a hollow body to discharge the lower airflow to an exterior of the engine room, wherein a left-right pair of vertical plates (40, 41) extending in a front-rear direction are provided on the floor, a specific vertical plate of the left-right pair of vertical plates being disposed on the exhaust side of the engine room, characterized in that a discharge port is provided in a part of the floor on the exhaust side and on a downstream side of the lower airflow relative to the specific vertical plate, the exhaust duct is disposed on the exhaust side of the engine room and provided on the floor on a downstream side of the lower airflow relative to the specific vertical plate, and has an air inlet provided in an upper portion of the exhaust duct, an air outlet provided in a lower portion of the exhaust duct and communicating with the discharge port and a part between the air inlet and the air outlet, the part forming an air passage to allow an air passed through the ventilation gap and flowed over an upper end of the specific vertical plate to be flowed from the air inlet to the air outlet and discharged through the discharge port while shielding the hydraulic pump from the discharge port. an engine room; a floor constituting a bottom surface of the engine room; an engine provided in the engine room such that a ventilation gap is formed below the engine; a hydraulic pump provided in the engine room on an exhaust side serving as one side of the engine in a left-right direction; a fan which is provided in the engine room on an intake side serving as an opposite side of the engine to the hydraulic pump, and which, when the fan is rotated, generates a cooling airflow that includes a lower airflow passing through the ventilation gap and flows from the intake side to the exhaust side; and an exhaust duct formed of a hollow body to discharge the lower airflow to an exterior of the engine room, wherein a left-right pair of vertical plates (40, 41) extending in a front-rear direction are provided on the floor, a specific vertical plate of the left-right pair of vertical plates being disposed on the exhaust side of the engine room, characterized in that a discharge port is provided in a part of the floor on the exhaust side and on a downstream side of the lower airflow relative to the specific vertical plate, the exhaust duct is disposed on the exhaust side of the engine room and provided on the floor on a downstream side of the lower airflow relative to the specific vertical plate, and has an air inlet provided in an upper portion of the exhaust duct, an air outlet provided in a lower portion of the exhaust duct and communicating with the discharge port and a part between the air inlet and the air outlet, the part forming an air passage to allow an air passed through the ventilation gap and flowed over an upper end of the specific vertical plate to be flowed from the air inlet to the air outlet and discharged through the discharge port while shielding the hydraulic pump from the discharge port.