Abstract: In a data transfer apparatus, as one substation in a loop type signal transfer system, e.g. for use in an automatic machine, synchronization information and address information are received and the address is checked by an address coincidence circuit; when address coincidence is detected the data information in the received signal is replaced by serialized data which is contrived by parallel-serial conversion of the parallel input data at the substation; therefore there is no need of once storing the entire received signal transferred, and therefore, high speed data transfer results.