PURPOSE: To reduce a required time by stabilizing a test and at the same time to record and store a record result easily by testing a controller with a computer according to a simulation program for executing a preset test procedure program and the simulation operation of an engine.

CONSTITUTION: It is judged whether a test is a new test or a continuous test and then an internal data is initialized in the case of the new test and an existing data is taken into a memory 13 in the case of the continuous data. Test items are displayed on a display 15 and test items are selected by a keyboard 17. When the selected item is a test, engine simulation operation corresponding to the test item is activated by a CPU 12 and an engine movement simulating the functions of a controller 1B is simulated. Therefore, a signal which is output by the engine is simulated and is input to the controller 1B as if the engine is in operation. Then, commands, etc., which are output from the controller 1B corresponding to the simulation operation are taken into a computer 11, thus judging whether a normal reaction is achieved or not.