PURPOSE: To execute and stop a program and to trace the executing condition with the low cost without needing a special hardware by equipping with a microprocessor device having a prescribed function.

CONSTITUTION: In a microprocessor device 2, when a command input from an input output device 5 is analyzed by a command input analyzing means 8 and the command of the execution control is analyzed, an execution control means 9 executes each one instruction until the stopping conditions satisfy a debugged program 11. By the result, it is decided whether the execution of the debugged program 11 is continued or stopped, the execution passing of the debugged program 11 is stored by a prescribed memory device and the setting of the stopping conditions of the debugged program 11, the setting of the execution condition to record, the execution condition, the execution passing, etc., are displayed by a condition setting displaying means 10. Thus, without needing the special hardware, the device can be cheaply composed by a hardware in a target board 1 held by a general purpose microprocessor application board.