A Distributed Denial of Service (DDoS) attack detection and defense apparatus and method are provided. The Distributed Denial of Service (DDoS) attack detection and defense apparatus includes: a flow information collection unit to collect, from one or more input packets with an IP address of an attack target system as a destination IP address, flow information including source IP addresses of the input packets and packet counts of one or more flows that are classified for each of the source IP addresses and each of different protocol types; an inspection unit to calculate packets per second (PPS) values of the flows based on the packet counts; and a response unit to determine a DDoS attack response method for each of the flows based on the PPS value and the protocol type of a corresponding flow and to process the corresponding flow using the determined DDoS attack response method.