A data processing device which can communicate with a computer terminal, comprises: a receiver to receive data transmitted from the computer terminal; a shifter to shift a state of the data processing device to a power saving state, after elapse of a predetermined time; and a releaser to release the power saving state according to specific data transmitted from the computer terminal, wherein, after the power saving state was released by the releaser, when the received data is first kind of data, the shifter shifts the data processing device to the power saving state after elapse of a first predetermined time, and, when the data received by the receiver is second kind of data different from the first kind of data, the shifter shifts the data processing device to the power saving state after elapse of a second predetermined time different from the first predetermined time.