PURPOSE: To automatically execute the dynamic verification of a protocol without necessitating a special practical environment or a simulation environment.

CONSTITUTION: This device is provided with a simulation environment setting part 10 for setting a simulation environment required for executing the dynamic verification of a communication protocol, through an input from a user, a simulation executing part 11 for executing the dynamic verification of the communication protocol on the set simulation environment, based on a state transition diagram, and a display control part 12 for displaying the present simulation state, that is, the state transition diagram and the simulation environment of the protocol being in the course of simulation at present, and moreover, the generation part of a protocol error and the error contents, etc., so as to be easily understandable to a user.