To appropriately discover fraudulent actions using a button or the like operable by a general player.

A prescribed period immediately before a big winning is set as a period under consideration (S380 and S382) on the basis of the history information of big winning signals received from a pachinko game machine and variation shortening signals accompanying the operation of a variation shortening switch, the continuous ON time and the number of times of ON of the variation shortening signals are computed on the basis of the history information of the variation shortening signals in the period under consideration and whether they are a normal value or an abnormal value is judged (step S384 and S386). The operation contents of a variation shortening switch are judged as a normal operation when both of them are the normal value (S388), and they are judged as an abnormal operation when one of them is the abnormal value (S390). As a result, the fraudulent actions using the variation shortening switch or the like operable by the general player are appropriately discovered.