A packet processing apparatus receiving a packet includes a memory storing a flow information, and a processor coupled to the memory and configured to, when a processing method for the received packet is defined in the flow information, store the packet into a buffer in the packet processing apparatus and process the packet stored in the buffer using the processing method, when the processing method is not defined in the flow information and a utilization rate of the buffer exceeds a threshold value, transmit the packet to another packet processing apparatus, and when the processing method is not defined in the flow information and the utilization rate of the buffer does not exceed the threshold value, store the packet into the buffer and issue an inquiry about the processing method.