Provided is a construction machine that is capable of securing a maintenance space above a hydraulic pump while enabling a NOx-reducing catalyst to be installed, not involving a significant increase in cost. The construction machine includes: a frame; an engine installed on the frame; a hydraulic pump adapted to be driven by the engine; a guard panel disposed on the frame to surround an engine room and having a maintenance port for the hydraulic pump; an exhaust-gas-purification device provided inside the engine room and connected to the engine via an exhaust pipe; and a support member adapted to support an exhaust-gas-aftertreatment device including the exhaust-gas-purification device, inside the engine room at a position just above the hydraulic pump. The support member has a purification device supporting portion to support the exhaust-gas-purification device and a catalyst supporting portion to support a NOx-reducing catalyst which is additionally included in the exhaust-gas-aftertreatment device, at a position closer to the maintenance port than the exhaust-gas-purification device. The catalyst supporting portion is adapted to support the NOx-reducing catalyst at a position higher than the exhaust-gas-purification device so as to form, over the hydraulic pump, a maintenance space having an upper end at a position higher than an upper end of a space formed under the purification device supporting portion and the exhaust-gas-purification device.