This study is showed reliability and validity of item of measurement to measuring authenticity of cultural tourism festival. And more over, authenticity of Gwangallieobang festival, one of the Busan cultural tourism festivals was researched experientially. Four general conclusions were drawn from the results of the research. (1) 15 items were selected to measuring authenticity of cultural tourism festival. and, it was constructed 3 factors of Objective authenticity, Experiential authenticity and Constructive authenticity; (2) Perceived level of authenticity(seven point scale) on Gwangalli-eobang festival by the visitors were output average 4.92 point for Objective authenticity, 4.37 point for Constructive authenticity and 4.24 point for Experiential authenticity; (3) Result of cluster analysis about authenticity of Gwangalli-eobang festival is showed two clusters; (4) Result of correlation analysis between demography characteristics, age and marriage status, and authenticity clusters found to be significantly related. The singles in twenty group gave highest authenticity rating and reversely the married people in thirty group gave lowest authenticity rating to Gwangalli-eobang festival.