Device detection is performed by using a second detection unit which uses unicast transmission with a destination address being changed in addition to a first detection unit which uses broadcasting/multicasting. When unicast transmission can be normally performed, detection using the first detection unit is performed to determine whether broadcasting/multicasting at this point of time can be performed. In addition, the first or second detection unit is selected or the processing order of the first and second detection units is changed in accordance with the permission/inhibition determination result.