This paper intends to introduce the development of a terminal agent for QoS measurement that is suitable for an NGN environment, and to summarize the results of its performance test. Using the terminal agent for service quality measurement, it is possible to measure the QoE-based end-toend service quality of voice phone, video phone, and VoD services. In addition, the terminal agent, installed in the user terminal (IP-based audio and video phones), as a software or hardware chip, measures the quality index for voice and video related multimedia services, such as R-value, MOS value, call success rate, one-way delay, jitter, packet loss, resolution. The terminal agent also applies the packet capturing method when using the actual service, and analyzes SIP, RTP, and RTCP protocol headers of the received packet. When the terminal agent was implemented in the IP video phone and compared with the performance of a general QoS measurement tool, there were barely any errors in the measurement v...