Disclosed herewith is a packet transfer apparatus that carries out 1+1 protection switching for traffics to be received variably in both length and cycle. The apparatus enables flows to be multiplexed and the link usage efficiency to be improved without generating any buffer overflow errors. The data transfer apparatus, upon receiving the third sequentially numbered data from the first communication route before receiving the preceding second sequentially numbered data, stores the received third data in a buffer. And upon receiving the second sequentially numbered data from the second communication route, the apparatus sends the second and third data sequentially. Then, upon receiving the third sequentially numbered data from the second communication route before receiving the second sequentially numbered data, the apparatus sends the third data when a predetermined waiting time expires.