A packet relay method and device in which even in the presence of a relay device between transmitting and receiving devices, a normality of a protection route can be surely confirmed is provided; A specific source address or destination address are registered, and when a route normality confirmation packet having the source address or destination address is received, the packet is transmitted to a protection route regardless of a hash operation; The registering can include link aggregation information in addition to the source address or destination address and the transmitting is made when the route normality confirmation packet consistent with both of the source address or destination address and the link aggregation information is received.