A paper-sheet authentication apparatus that is configured to determine an authenticity and preferably a kind of a paper sheet having a characteristic to emit phosphorescence when irradiated with an excitation light, comprising: a transport unit that is configured to transport the paper sheet; an excitation-light irradiating unit that is configured to irradiate with the excitation light a plurality of small areas of the paper sheet being transported by the transport unit, wherein the excitation-light irradiating unit is comprised of a plurality of the excitation-light irradiating units which are arranged in a direction of an intersection line of a surface parallel to a transport surface of the paper sheet and a surface orthogonal to a transport direction of the paper sheet; a phosphorescence-intensity acquiring unit that is configured to acquire a phosphorescence intensity a plurality of times from each of the plurality of small areas on the paper sheet after the excitation-light irradiating unit has irradiated the corresponding small areas of the paper sheet with the excitation light and then stopped irradiating wherein the same number of the phosphorescence-intensity acquiring units as the number of the excitation-light irradiating units are arranged in the same direction as the direction in which the excitation-light irradiating units are arranged and wherein the transport unit is configured to transport the paper sheet at a speed such that the phosphorescence-intensity acquiring units receive the afterglow from at least 50% or more of the region in which the excitation light was irradiated; a phosphorescence decay-rate calculating unit that is configured to calculate a decay rate indicating a decrease rate of the phosphorescence intensity of each of the small areas on the paper sheet based on the phosphorescence intensity acquired a plurality of times by the phosphorescence-intensity acquiring unit from the small areas on the paper sheet; a phosphorescence decay-rate pattern generating unit that is configured to generate a phosphorescence decay-rate pattern in which the decay rate calculated by the phosphorescence decay-rate calculating unit is associated with the positions of the respective small areas on the paper sheet based on a transport state of the paper sheet transported by the transport unit; and an authentication unit that is configured to determine the authentication of the paper sheet targeted for determination by comparing a previously generated phosphorescence decay-rate pattern of a genuine paper sheet with the phosphorescence decay-rate pattern of the paper sheet targeted for determination generated by the phosphorescence decay-rate pattern generating unit. a transport unit that is configured to transport the paper sheet; an excitation-light irradiating unit that is configured to irradiate with the excitation light a plurality of small areas of the paper sheet being transported by the transport unit, wherein the excitation-light irradiating unit is comprised of a plurality of the excitation-light irradiating units which are arranged in a direction of an intersection line of a surface parallel to a transport surface of the paper sheet and a surface orthogonal to a transport direction of the paper sheet; a phosphorescence-intensity acquiring unit that is configured to acquire a phosphorescence intensity a plurality of times from each of the plurality of small areas on the paper sheet after the excitation-light irradiating unit has irradiated the corresponding small areas of the paper sheet with the excitation light and then stopped irradiating wherein the same number of the phosphorescence-intensity acquiring units as the number of the excitation-light irradiating units are arranged in the same direction as the direction in which the excitation-light irradiating units are arranged and wherein the transport unit is configured to transport the paper sheet at a speed such that the phosphorescence-intensity acquiring units receive the afterglow from at least 50% or more of the region in which the excitation light was irradiated; a phosphorescence decay-rate calculating unit that is configured to calculate a decay rate indicating a decrease rate of the phosphorescence intensity of each of the small areas on the paper sheet based on the phosphorescence intensity acquired a plurality of times by the phosphorescence-intensity acquiring unit from the small areas on the paper sheet; a phosphorescence decay-rate pattern generating unit that is configured to generate a phosphorescence decay-rate pattern in which the decay rate calculated by the phosphorescence decay-rate calculating unit is associated with the positions of the respective small areas on the paper sheet based on a transport state of the paper sheet transported by the transport unit; and an authentication unit that is configured to determine the authentication of the paper sheet targeted for determination by comparing a previously generated phosphorescence decay-rate pattern of a genuine paper sheet with the phosphorescence decay-rate pattern of the paper sheet targeted for determination generated by the phosphorescence decay-rate pattern generating unit.