A construction machine comprising: an engine; an air cleaner having an exhaust port connected to the engine and having a cylindrical outer peripheral surface, the air cleaner configured to filter air taken in by the engine; and an air intake pipe interconnecting the exhaust port of the air cleaner and the engine, wherein: the air cleaner is placed in a posture where the exhaust port faces a side opposite to the engine; the air intake pipe includes a connection end portion to be connected to the exhaust port, a return portion having a shape extending from the connection end portion and returning toward the engine side, and an engine-side portion extending from a distal end of the return portion toward the engine along the air cleaner, thus forming a returning pipe at an exhaust side of the air cleaner; the air intake pipe has a downstream-side portion which is arranged so as to locate at least a part of the downstream-side portion in a space between the cylindrical outer peripheral surface of the air cleaner and a restriction plane extending in a tangent direction of the cylindrical outer peripheral surface to restrict a position of the air cleaner, characterized in that the restriction plane is a horizontal air-cleaner placement plane, on which the air cleaner is placed; and the downstream-side portion is arranged in a space defined between the outer peripheral surface of the air cleaner and the air-cleaner placement plane obliquely below the air cleaner when the air cleaner is viewed from the side. an engine; an air cleaner having an exhaust port connected to the engine and having a cylindrical outer peripheral surface, the air cleaner configured to filter air taken in by the engine; and an air intake pipe interconnecting the exhaust port of the air cleaner and the engine, wherein: the air cleaner is placed in a posture where the exhaust port faces a side opposite to the engine; the air intake pipe includes a connection end portion to be connected to the exhaust port, a return portion having a shape extending from the connection end portion and returning toward the engine side, and an engine-side portion extending from a distal end of the return portion toward the engine along the air cleaner, thus forming a returning pipe at an exhaust side of the air cleaner; the air intake pipe has a downstream-side portion which is arranged so as to locate at least a part of the downstream-side portion in a space between the cylindrical outer peripheral surface of the air cleaner and a restriction plane extending in a tangent direction of the cylindrical outer peripheral surface to restrict a position of the air cleaner, characterized in that the restriction plane is a horizontal air-cleaner placement plane, on which the air cleaner is placed; and the downstream-side portion is arranged in a space defined between the outer peripheral surface of the air cleaner and the air-cleaner placement plane obliquely below the air cleaner when the air cleaner is viewed from the side. the air cleaner is placed in a posture where the exhaust port faces a side opposite to the engine; the air intake pipe includes a connection end portion to be connected to the exhaust port, a return portion having a shape extending from the connection end portion and returning toward the engine side, and an engine-side portion extending from a distal end of the return portion toward the engine along the air cleaner, thus forming a returning pipe at an exhaust side of the air cleaner; the air intake pipe has a downstream-side portion which is arranged so as to locate at least a part of the downstream-side portion in a space between the cylindrical outer peripheral surface of the air cleaner and a restriction plane extending in a tangent direction of the cylindrical outer peripheral surface to restrict a position of the air cleaner, characterized in that the restriction plane is a horizontal air-cleaner placement plane, on which the air cleaner is placed; and the downstream-side portion is arranged in a space defined between the outer peripheral surface of the air cleaner and the air-cleaner placement plane obliquely below the air cleaner when the air cleaner is viewed from the side.