A debugging device and method are provided, including a central processing unit (CPU) connected to a chipset with a system management interrupt pin. The debugging method includes sending out a system management interrupt signal to central processing unit from the system management interrupt pin of the chipset. Then the CPU moves into a system management mode and pops out a debugging operation window for selecting and executing each debugging item. After the execution of each debugging item is completed, the CPU will leave the debugging operation window and return to the next instruction before debugging. After the execution of each debugging item is completed in the debugging operation window, the CPU will return to the operation system and continue the execution of next instruction before debugging. The execution of debugging will not influence the status and the program execution from the operating system. The disclosed debugging method is convenient for executing each debugging item at any time.