A construction machine comprising: a centrifugal fan housed inside a machine body; and a bell mouth arranged on a suction side of the centrifugal fan, the bell mouth having an outlet, the centrifugal fan including a hub that is rotatable around a rotation axis, an annular shroud arranged so as to face the hub, the shroud forming a flow path between the shroud and the hub, the shroud having a suction port, and a plurality of blades provided between the hub and the shroud at intervals in a circumferential direction, each of the plurality of blades including a leading edge on a side where air flows in, a trailing edge on a side where air flows out, a pressure surface that is one of blade surfaces extending between the leading edge and the trailing edge, the pressure surface facing forward relative to a rotation direction, and a suction surface that is another of the blade surfaces extending between the leading edge and the trailing edge, the suction surface facing backward relative to the rotation direction, the outlet of the bell mouth being arranged on a radially inner side of the suction port of the shroud, wherein each of the plurality of blades is formed such that the leading edge has a convex shape protruding toward the suction surface relative to a line segment linking a connection of the leading edge with the hub and a connection of the leading edge with the shroud, and a vertex of the convex shape of the leading edge is positioned on a radially inner side of a wall surface of the outlet of the bell mouth when the suction side of the centrifugal fan is seen in an axis direction, characterized in that each of the plurality of blades is formed such that the convex shape of the leading edge extends to the trailing edge, and each of the plurality of blades is formed such that a curvature at the vertex of the convex shape of each of the plurality of blades gradually increases from the leading edge toward a midway position disposed between the leading edge and the trailing edge and gradually decreases from the midway position toward the trailing edge. a centrifugal fan housed inside a machine body; and a bell mouth arranged on a suction side of the centrifugal fan, the bell mouth having an outlet, the centrifugal fan including a hub that is rotatable around a rotation axis, an annular shroud arranged so as to face the hub, the shroud forming a flow path between the shroud and the hub, the shroud having a suction port, and a plurality of blades provided between the hub and the shroud at intervals in a circumferential direction, a hub that is rotatable around a rotation axis, an annular shroud arranged so as to face the hub, the shroud forming a flow path between the shroud and the hub, the shroud having a suction port, and a plurality of blades provided between the hub and the shroud at intervals in a circumferential direction, each of the plurality of blades including a leading edge on a side where air flows in, a trailing edge on a side where air flows out, a pressure surface that is one of blade surfaces extending between the leading edge and the trailing edge, the pressure surface facing forward relative to a rotation direction, and a suction surface that is another of the blade surfaces extending between the leading edge and the trailing edge, the suction surface facing backward relative to the rotation direction, a leading edge on a side where air flows in, a trailing edge on a side where air flows out, a pressure surface that is one of blade surfaces extending between the leading edge and the trailing edge, the pressure surface facing forward relative to a rotation direction, and a suction surface that is another of the blade surfaces extending between the leading edge and the trailing edge, the suction surface facing backward relative to the rotation direction, the outlet of the bell mouth being arranged on a radially inner side of the suction port of the shroud, wherein each of the plurality of blades is formed such that the leading edge has a convex shape protruding toward the suction surface relative to a line segment linking a connection of the leading edge with the hub and a connection of the leading edge with the shroud, and a vertex of the convex shape of the leading edge is positioned on a radially inner side of a wall surface of the outlet of the bell mouth when the suction side of the centrifugal fan is seen in an axis direction, characterized in that the leading edge has a convex shape protruding toward the suction surface relative to a line segment linking a connection of the leading edge with the hub and a connection of the leading edge with the shroud, and a vertex of the convex shape of the leading edge is positioned on a radially inner side of a wall surface of the outlet of the bell mouth when the suction side of the centrifugal fan is seen in an axis direction, characterized in that each of the plurality of blades is formed such that the convex shape of the leading edge extends to the trailing edge, and each of the plurality of blades is formed such that a curvature at the vertex of the convex shape of each of the plurality of blades gradually increases from the leading edge toward a midway position disposed between the leading edge and the trailing edge and gradually decreases from the midway position toward the trailing edge.