A construction machine comprising: a lower traveling body; an upper frame slewably provided on the lower traveling body; a rear wall portion provided at a rear portion of the upper frame to cover a space over the upper frame from therebehind, the rear wall portion having a curved portion curved in an approximately arc shape in top plan view to serve as a right or left end thereof; an engine provided on the upper frame at a position in front of the rear wall portion in such a manner that an interspace is formed between the engine and the curved portion; and an exhaust aftertreatment device configured to treat exhaust gas of the engine, and provided in front of the rear wall portion while being superposed over the interspace, the exhaust aftertreatment device comprising a first treatment section capable of removing a first component contained in the exhaust gas, and a second treatment section capable of removing a second component contained in the exhaust gas, wherein the first treatment section and the second treatment section are supported over the upper frame in a posture where respective longitudinal directions (J2, J3) thereof are oriented parallel to each other in top plan view, characterized in that the first treatment section and the second treatment section are supported over the upper frame in a posture where the respective longitudinal directions (J2, J3) thereof are oriented along the curved portion in top plan view, wherein the longitudinal directions (J2, J3) of the first and second treatment sections (23, 24) are also inclined with respect to the front-rear direction in such a manner that right or left side portions of the first and second treatment sections (23, 24) are located more forwardly than left or right side portions thereof in top plan view. a lower traveling body; an upper frame slewably provided on the lower traveling body; a rear wall portion provided at a rear portion of the upper frame to cover a space over the upper frame from therebehind, the rear wall portion having a curved portion curved in an approximately arc shape in top plan view to serve as a right or left end thereof; an engine provided on the upper frame at a position in front of the rear wall portion in such a manner that an interspace is formed between the engine and the curved portion; and an exhaust aftertreatment device configured to treat exhaust gas of the engine, and provided in front of the rear wall portion while being superposed over the interspace, the exhaust aftertreatment device comprising a first treatment section capable of removing a first component contained in the exhaust gas, and a second treatment section capable of removing a second component contained in the exhaust gas, wherein the first treatment section and the second treatment section are supported over the upper frame in a posture where respective longitudinal directions (J2, J3) thereof are oriented parallel to each other in top plan view, characterized in that the first treatment section and the second treatment section are supported over the upper frame in a posture where the respective longitudinal directions (J2, J3) thereof are oriented along the curved portion in top plan view, wherein the longitudinal directions (J2, J3) of the first and second treatment sections (23, 24) are also inclined with respect to the front-rear direction in such a manner that right or left side portions of the first and second treatment sections (23, 24) are located more forwardly than left or right side portions thereof in top plan view.