1. A monitoring system comprising an information processing device for acquiring a facial image and a monitoring device for performing monitoring processing based on an image supplied from said information device, wherein said information processing device comprises: acquisition means for acquiring a facial image of an individual who approaches a game machine as a facial image of a collation object; collation object storage means for storing a predetermined number of facial images of said collation object; condition information extraction means for extracting condition information which indicates conditions for extracting characteristic value of said facial image based on the facial image of said collation object acquired by said acquisition means and the facial image of the collation object stored by said collation object storage means; condition information comparison means for comparing the condition information on the facial image acquired by said acquisition means and the condition information on the facial image of the collation object stored by said collation object storage means, based on the condition information extracted by said condition information extraction means; and transmission means for sending the facial image acquired by said acquisition means to said monitoring device when the condition information on the facial image acquired by said acquisition means is better than the condition information on the facial image of the collation object stored by said collation object storage means according to said condition information comparison means, wherein said monitoring device comprises: reception means for receiving the facial image of said collation object which is sent by said transmission means; storage means for storing the facial image of a registered individual in a registered individual database; first similarity collation means for calculating a similarity of the facial image of the collation object received by said reception means and the facial image of the registered individual stored by said storage means, and performing collation; first similarity judgment means for judging whether the facial image of said collation object is the facial image of said registered individual by comparing the similarity which is a collation result of said first similarity collation means and a predetermined threshold; notification means for notifying that said collation object is said registered individual when the facial image of said collation object is the facial image of said registered individual based on a judgment result of said first similarity judgment means; and update means wherein when the condition information on the facial image acquired by said acquisition means is better than the condition information on the facial image of the collation object stored by said collation object storage means according to said condition information comparison means, said collation object storage section is updated by deleting a facial image of which said condition information is lowest from a predetermined number of facial images stored in said collation object storage means, and storing the facial image acquired by said acquisition means as a facial image of said collation object.