Provided is a construction machine which is capable of stably support an exhaust aftertreatment device comprising a first treatment section and a second treatment section arranged in one-above-the-other and side-by-side relation. A hydraulic excavator comprises: an exhaust aftertreatment device comprising a first treatment section and a second treatment section which are arranged in one-above-the-other and in side-by-side relation; a lower plate attached to a lower surface of the exhaust aftertreatment device, and provided above a slewing frame to support the exhaust aftertreatment device from therebeneath in such a manner that the exhaust aftertreatment device is disposed at a position overlapping the engine in side view; and a left vertical plate disposed to extend upwardly from a portion of the lower plate located between the exhaust aftertreatment device and the engine, and attached to a lateral surface of the exhaust aftertreatment device.