In a method of and an apparatus for transferring supplementary paper money in an automatic teller machine that includes a paper-money processing mechanism that has a plurality of transport routes formed among the paper-money that provide a path between a plurality of paper-money containers, a cassette storing a supplementary money supply and a paper-money discriminator part for transporting paper money. A plurality of changeover gates are provided at the forks of the transport routes for changing the destination of paper money, and a control part for controlling the transportation routes and the changeover gates. The method and apparatus optimize the transfer of supplementary paper-money, and a control part for controlling the transport routes and the changeover gates. The method and apparatus optimize the transfer of supplementary paper-money by checking for times in which the paper-money processing mechanism, especially the transport routes, are not in use.