A software update device capable of communicating with a target update device via a network, the software update device including: a certification information setting unit for generating a first certification information, and transmitting the first certification information to the target update device via a first communication path; a certification requesting unit for transmitting a second certification information to the target update device, and requesting the target update device to execute a certification process with the first and second certification information; and a transmitting unit for transmitting an update software for updating a software of the target update device to the target update device via a second communication path when the certification process succeeds, the second communication path having a process load less than that of the first communication path.