A packet relay apparatus identifies port information for identifying a port, included in a partition corresponding to a reception port having received a packet, from a partition information storing unit which stores a correspondence between port information for identifying ports included in the partition and partition information for identifying the partition configured for the apparatus. The apparatus determines whether the identified port information is included in the port information stored by being corresponded to reception VLAN information which is VLAN information set for a received packet by a VLAN information storing unit which is a storing unit storing a correspondence between port information for identifying a port used for transmission and/or reception of a packet transmitted and VLAN information for identifying the virtual network. The apparatus transmits the packet from a port determined to include the port information in response to the determination that the port information is included.