A structure maintains a gap in a paper money discriminating apparatus that may be provided in an automatic teller machine. The structure may include a paper money discriminating sensor that is provided in an upper body to discriminate whether a paper money to be conveyed along a conveyance path is counterfeit money, a lower body that is provided so as to face the paper money discriminating sensor with a predetermined gap therebetween, and spacing protrusions that protrude upward from an upper surface of the lower body and come in contact with both end portions of the paper money discriminating sensor so as to maintain a constant gap between a lower surface of the paper money discriminating sensor and the upper surface of the lower body.