An objective of the present invention is to provide an assembly system capable of reducing the equipment space while various kinds of automotive parts are assembled on one production line. The assembly system assembles plural kinds of automotive parts consisting of a main body and a part to be installed to the main body. This assembly system comprises an operator area at which an operator is assigned, a plurality of travel carts on which a main body of each of automotive parts is placed, traveling along the operator area, a part pallet on which a part to be installed to each of the automotive parts is placed, a belt conveyer conveying this part pallet along the operator area, and a control device controlling thereof. The control device drives the travel carts and the belt conveyer so as to convey the travel carts and the part pallet synchronously.