PURPOSE: To automatically generate the state transition diagram from a state transition table by reading in successively each row of the state transition table, entering a before-transition state name and an after-transition state name in different columns and displaying them so as to connect an arc for showing the transition.

CONSTITUTION: A before-transition state name of a state transition table stored in a state transition table storage means 101, and an after-transition state name are read in a before-transition state name placing/calculating means 102, and an after- transition state name placing/calculating means 104, respectively, and the respective positions are calculated, and stored in a before-transition state name placing/storage means 103 and an after-transition state name placing/storage means 105. Subsequently, by an arc placing means 106, a start point and an end point of an arc for showing the transition are calculated, and with regard to one row which is read in, an arc for showing a before-transition state name and an after-transition state name which are determined and the transition is outputted onto an output means 107, and a processing of all rows of the state transition table is executed. According to this configuration, an easily visible state transition diagram can be generated automatically from the state transition table.