A method of using a general-purpose microprocessor to debug a programmable logic controller is provided, the method including: at a MPU of the PLC, backing up identification information and file information of a interrupt step of steps contained in a user's program and substituting the interrupt step with an exceptional interrupt code to set the interrupt step for the debugging; and at the MPU of the PLC, interrupting the driving of the PLC at a step having the exceptional interrupt code in executing the user's program step by step while driving the PLC.