A construction machine comprising: a vehicle body frame for supporting an engine; an exhaust gas aftertreatment device connected to an exhaust system of the engine; and an aftertreatment device mount for supporting the exhaust gas aftertreatment device, wherein the aftertreatment device mount includes a top plate, characterised in that the top plate includes: a pair of placement portions that extend in a first direction being horizontal, are spaced apart from each other in a second direction intersecting with the first direction and a vertical direction, and include placement surfaces on which the exhaust gas aftertreatment device is allowed to be placed, each of the placement surfaces of the pair of placement portions being provided with a connecting portion connected to the exhaust gas aftertreatment device at one or more predetermined positions in the first direction; a groove portion that is disposed between the pair of placement portions and connects the pair of placement portions to each other, the groove portion including a bottom disposed at a position lower than the placement surface and a pair of inner walls connecting the pair of placement surfaces to the bottom; a pair of outer walls that are connected to both side edges of the pair of placement portions in the second direction and extend in the first direction, the pair of outer walls being disposed to face the pair of inner walls in the second direction; and at least one reinforcing member disposed to extend in the second direction at a position corresponding to the connecting portion in the first direction, and the at least one reinforcing member includes a pair of first reinforcing portions that are disposed on the placement surfaces of the pair of placement portions and are sandwiched between the placement surfaces and the exhaust gas aftertreatment device; and at least one second reinforcing portion that is fitted in the groove portion and connects the pair of first reinforcing portions in the second direction. a vehicle body frame for supporting an engine; an exhaust gas aftertreatment device connected to an exhaust system of the engine; and an aftertreatment device mount for supporting the exhaust gas aftertreatment device, wherein the aftertreatment device mount includes a top plate, a pair of placement portions that extend in a first direction being horizontal, are spaced apart from each other in a second direction intersecting with the first direction and a vertical direction, and include placement surfaces on which the exhaust gas aftertreatment device is allowed to be placed, each of the placement surfaces of the pair of placement portions being provided with a connecting portion connected to the exhaust gas aftertreatment device at one or more predetermined positions in the first direction; a groove portion that is disposed between the pair of placement portions and connects the pair of placement portions to each other, the groove portion including a bottom disposed at a position lower than the placement surface and a pair of inner walls connecting the pair of placement surfaces to the bottom; a pair of outer walls that are connected to both side edges of the pair of placement portions in the second direction and extend in the first direction, the pair of outer walls being disposed to face the pair of inner walls in the second direction; and at least one reinforcing member disposed to extend in the second direction at a position corresponding to the connecting portion in the first direction, and the at least one reinforcing member includes a pair of first reinforcing portions that are disposed on the placement surfaces of the pair of placement portions and are sandwiched between the placement surfaces and the exhaust gas aftertreatment device; and at least one second reinforcing portion that is fitted in the groove portion and connects the pair of first reinforcing portions in the second direction.