A load reducing system comprising: a switch (20, 20-1, 20-2, 20-3) configured to carry out processing of a received packet based on a flow entry defining a rule and an action to uniformly control packets as a flow; and a controller configured to set the flow entry to said switch (20, 20-1, 20-2, 20-3), wherein when receiving a given packet, said switch (20, 20-1, 20-2, 20-3) carries out an inquiry of a flow entry corresponding to the received given packet to said controller, if the flow entry corresponding to the received given packet is not set, stacks the received given packet, and controls a transfer of one of the packets which has a same header data as the stacked packet by using the stacked packet, until the flow entry corresponding to the received packet is set; wherein when receiving a packet before the flow entry is set, said switch (20, 20-1, 20-2, 20-3) checks whether or not a packet which has the same header data as the received packet is stacked, and when the packet which has the same header data as the received packet is stacked, said switch (20, 20-1, 20-2, 20-3) broadcasts the stacked packet, and newly stacks the received packet; and when the packet which has the same header data as the received packet has not been stacked, said switch (20, 20-1, 20-2, 20-3) checks whether or not the received packet is a broadcasted packet, and if the received packet is not a broadcasted packet, said switch (20, 20-1, 20-2, 20-3) carries out an inquiry of the flow entry corresponding to the received packet to said controller, and stacks the received packet, and if the received packet is a broadcasted packet, said switch (20, 20-1, 20-2, 20-3) checks whether or not the packet which has the same header data as the received packet has been set as a broadcast object packet, and if the packet which has the same header data as the received packet has not been set as the broadcast object packet, said switch (20, 20-1, 20-2, 20-3) sets the received packet as the broadcast object packet, and broadcasts the received packet. a switch (20, 20-1, 20-2, 20-3) configured to carry out processing of a received packet based on a flow entry defining a rule and an action to uniformly control packets as a flow; and a controller configured to set the flow entry to said switch (20, 20-1, 20-2, 20-3), wherein when receiving a given packet, said switch (20, 20-1, 20-2, 20-3) carries out an inquiry of a flow entry corresponding to the received given packet to said controller, if the flow entry corresponding to the received given packet is not set, stacks the received given packet, and controls a transfer of one of the packets which has a same header data as the stacked packet by using the stacked packet, until the flow entry corresponding to the received packet is set; wherein when receiving a packet before the flow entry is set, said switch (20, 20-1, 20-2, 20-3) checks whether or not a packet which has the same header data as the received packet is stacked, and when the packet which has the same header data as the received packet is stacked, said switch (20, 20-1, 20-2, 20-3) broadcasts the stacked packet, and newly stacks the received packet; and when the packet which has the same header data as the received packet has not been stacked, said switch (20, 20-1, 20-2, 20-3) checks whether or not the received packet is a broadcasted packet, and if the received packet is not a broadcasted packet, said switch (20, 20-1, 20-2, 20-3) carries out an inquiry of the flow entry corresponding to the received packet to said controller, and stacks the received packet, and if the received packet is a broadcasted packet, said switch (20, 20-1, 20-2, 20-3) checks whether or not the packet which has the same header data as the received packet has been set as a broadcast object packet, and if the packet which has the same header data as the received packet has not been set as the broadcast object packet, said switch (20, 20-1, 20-2, 20-3) sets the received packet as the broadcast object packet, and broadcasts the received packet.