driven by a motor 20 to rotate for transfer toward the tact conveyer 2 a returning lifter 21 is disposed at the terminal end of the first conveying device 6 and provided with a roller conveyer 24 which is supported by a pantograph 23 driven by a hydraulic mechanism 22 the roller conveyer 18 is moved up and down to be at a lower position d 39 aligned with the returning roller conveyer 6b and at an upper position u 39 aligned with the advancing roller conveyer 6a these positions d 39 and u 39 are detected by limit switches 25a and 25b respectively the roller conveyer 24 is driven by a motor 26 to rotate for transfer toward the main floor conveyer 4 sledges or pallets 28 on each of which the engine eg and the front suspension fs is loaded from the main floor conveyer 4 as the engine front suspension assembly eg fs are successively put on the roller conveyer 18 of the loading lifter 15 the pallet 28 on the roller conveyer 18 of the loading lifter 15 is forwarded to a position a and then through a position b to a position c on the advancing roller conveyer 6a and emptied at the position c then the pallet 28 is further sent to the roller conveyer 24 of the returning lifter 21 to be transferred to the returning roller conveyer 6b through the downward.