To provide a component assembly and conveyance system that can reduce the number of self-propelling conveyance carts, the size of a lift, the number of constituent devices as well as the man-hour for design.

The component assembly and conveyance system is constituted of a low-speed component assembly work line 1 comprising a chain conveyer 3 that circles along a suspension rail 2 and a high-speed conveyance line 11 comprising the self-propelling conveyance cart 13 of overhead traveling type that circulates along an elevated rail 12 at a high speed. Since a hanger is transferred by a lift type transferring device 17 and 17' installed at a transferring position 16 for an assembled product retaining hanger and a transferring position 19 for a vacant hanger, the self-propelling conveyance carts required are only the number of carts traveling on the high-speed conveyance line, thereby reducing the number of the self-propelling conveyance carts.