Recently embedded systems are used at various industrial domains. Especially a USN/RFID system is a one of the rising application domain. But by the reason of the small size, general embedded operating system is not applied to USN/RFID systems. Therefore the need of a tiny embedded operating system is increased. In order to provide the high flexibility and the efficient deployment of various systems, ETRI developed a scalable and reconfigurable OS named NanoQplus and integrated development environment named NanoEsto. NanoEsto that consists of various atomic tools enable users to develop the NanoQplus application easily. In this paper, we focus on the debugger that is one of the atomic tools of NanoEsto.