PURPOSE: To provide a stack pin holder circulating device for assembling a heat exchanger which fully automatically insert a pipe.

CONSTITUTION: The device is provided with a collecting pallet 27 on which plural stack pin holders on which stack pins are set and many fins are laminated are mounted in parallel. The device is also provided with a circulating path 26 including a transfer position B and an import position C for the collecting pallets, a carrying path 30 by which a pallet which carries the stack pin holders one by one is circulated between the transfer position and a pipe inserting part corresponding to point B on the circulating path and the import position corresponding to point C on the circulating path, a transfer device 25 by which the stack pin holders are transferred one by one from the collecting pallet at joint B to the pallet on the carrying path and an import device by which the empty stack pin holders from which the fins inserted with the pipes at the pipe inserting part are removed at point D are successively transferred to the collecting pallet at point C.