A data transfer device includes a serial interface including plural transmission paths and carrying out a data transfer operation with plural operating frequencies, transfer requesting units issuing a data transfer request to the serial interface, a request monitoring unit, a condition setting unit setting a set transmission path condition including at least one of a number of the transmission paths and an operating frequency used when the data transfer requests are issued to switch statuses of the data transfer requests to statuses of switching data transfer requests, a use transmission path condition determining unit determining the set transmission path condition corresponding to the status of the switching data transfer request as a use transmission path condition when the status of switching data transfer request corresponds to the status of data transfer request by comparing the statuses, and a switching unit switching to the use transmission path condition.