An intake structure for a vehicle-mounted internal combustion engine, including an air cleaner device having an air cleaner case compartmentalized by an air cleaner element into a non-purifying chamber (Ca) and a purifying chamber (Cb); wherein an intake pipe extending from a cylinder head of the internal combustion engine mounted on a vehicle and the purifying chamber (Cb) in the air cleaner case are held in fluid communication with each other by an intake joint passageway tube; wherein: the intake joint passageway tube is made up of an inner intake joint passageway tube disposed in the purifying chamber (Cb) in the air cleaner case and an outer intake joint passageway tube contiguous to the inner intake joint passageway tube; and characterised in that: the inner intake joint passageway tube is divided into two half joint passageway tubes (35U, 35D) combined together, along a plane including substantially a central axis of the inner intake joint passageway tube; and in that: the outer intake joint passageway tube extends out of the air cleaner case; the inner intake joint passageway tube has a plurality of bent portions on a central axis plane including the central axis of the inner intake joint passageway tube, and is made up of a pair of an upper half joint passageway tube and a lower half joint passageway tube combined together, which are divided by the central axis plane; the inner intake joint passageway tube has a downstream end fitted in an upstream end of the outer intake joint passageway tube which is fitted in the air cleaner case; the inner intake joint passageway tube has upper and lower downstream engaging teeth (35Up, 35Dp) engaging and coupled to upper and lower engaging tongues (36p, 36p) provided on the outer intake joint passageway tube; and the air cleaner case is provided with engaging protrusions (43U, 43D) having engaging pins (43Uq, 43Dq) on distal ends thereof, the engaging pins (43Uq, 43Dq) engaging in forwardly open engaging holes (35Uqh, 35Dqh) defined in upper and lower upstream engaging members (35Uq, 35Dq) on the inner intake joint passageway tube, thereby supporting the inner intake joint passageway tube. wherein an intake pipe extending from a cylinder head of the internal combustion engine mounted on a vehicle and the purifying chamber (Cb) in the air cleaner case are held in fluid communication with each other by an intake joint passageway tube; wherein: the intake joint passageway tube is made up of an inner intake joint passageway tube disposed in the purifying chamber (Cb) in the air cleaner case and an outer intake joint passageway tube contiguous to the inner intake joint passageway tube; and characterised in that: the inner intake joint passageway tube is divided into two half joint passageway tubes (35U, 35D) combined together, along a plane including substantially a central axis of the inner intake joint passageway tube; and in that: the outer intake joint passageway tube extends out of the air cleaner case; the inner intake joint passageway tube has a plurality of bent portions on a central axis plane including the central axis of the inner intake joint passageway tube, and is made up of a pair of an upper half joint passageway tube and a lower half joint passageway tube combined together, which are divided by the central axis plane; the inner intake joint passageway tube has a downstream end fitted in an upstream end of the outer intake joint passageway tube which is fitted in the air cleaner case; the inner intake joint passageway tube has upper and lower downstream engaging teeth (35Up, 35Dp) engaging and coupled to upper and lower engaging tongues (36p, 36p) provided on the outer intake joint passageway tube; and the air cleaner case is provided with engaging protrusions (43U, 43D) having engaging pins (43Uq, 43Dq) on distal ends thereof, the engaging pins (43Uq, 43Dq) engaging in forwardly open engaging holes (35Uqh, 35Dqh) defined in upper and lower upstream engaging members (35Uq, 35Dq) on the inner intake joint passageway tube, thereby supporting the inner intake joint passageway tube. the outer intake joint passageway tube extends out of the air cleaner case; the inner intake joint passageway tube has a plurality of bent portions on a central axis plane including the central axis of the inner intake joint passageway tube, and is made up of a pair of an upper half joint passageway tube and a lower half joint passageway tube combined together, which are divided by the central axis plane; the inner intake joint passageway tube has a downstream end fitted in an upstream end of the outer intake joint passageway tube which is fitted in the air cleaner case; the inner intake joint passageway tube has upper and lower downstream engaging teeth (35Up, 35Dp) engaging and coupled to upper and lower engaging tongues (36p, 36p) provided on the outer intake joint passageway tube; and the air cleaner case is provided with engaging protrusions (43U, 43D) having engaging pins (43Uq, 43Dq) on distal ends thereof, the engaging pins (43Uq, 43Dq) engaging in forwardly open engaging holes (35Uqh, 35Dqh) defined in upper and lower upstream engaging members (35Uq, 35Dq) on the inner intake joint passageway tube, thereby supporting the inner intake joint passageway tube.