To perform data transfer according to respective reception performance levels of peripherals when a plurality of peripherals are connected to a host device via a common lane.

A data processing device (1) includes a host device (10) having an interface, a first device (12) connected to the interface via a plurality of data lanes, and a second device (13) connected to the interface via a part of the data lanes in the plurality of data lanes. The interface transmits the data by adding dummy data to the actual data and distributing the data to the plurality of data lanes. When the actual data are acquired by one of the first and second devices, the other device is made to recognize that the actual data are insignificant data. Consequently, the data transfer is performed to the first and second devices according to their respective reception performance levels.