An online debug system for an information processing device is provided that enables easily connecting a debug device for online debugging to an information processing device while maintaining minimum required functions of the information processing device as a product. The online debug system has a debug device that transfers a directive from outside to thereby debug a navigation system. The navigation system includes a debug daemon that debugs the navigation system and a data expansion unit that reads a communication driver group stored in a USB memory via a connection terminal and validates it. A serial communication driver as the communication driver group validated in the navigation system enables the debug device communicate with the debug daemon.