An apparatus for measuring fluorescence lifetime includes a pulse laser source that generates a pulse excitation light, a detector that detects a fluorescence generated from a sample by irradiating the pulse excitation light, and outputs a detection signal corresponding to the fluorescence, a measurement unit that measures number of photons emitted in a predetermined time gate based on the detection signal, a correction unit that corrects the number of photons measured based on Poisson distribution, and a calculation unit that calculates the fluorescence lifetime of the sample based on the number of photons corrected.