A data transfer method for connecting a master unit on an upstream side and a plurality of slave units on an downstream side in series with serial bus by a daisy chain system and transferring data having an appended error check code or error correction code between a data transmitter and a data receiver, the data transfer method including: transferring the data flowing in the serial bus in the slave unit from the data transmitter to the data receiver without performing an error check or error correction; performing an error check of the data in a circuit provided in the slave unit aside from a circuit in which the data flow; and informing a result of the error check to the master unit individually by the slave unit, which has performed the error check of the data.