An integrating sphere photometer and a measuring method of the same are provided to precisely measure a directional light source. The integrating sphere photometer includes an integrating sphere having a plurality of through-holes, a plurality of photometers disposed at the through-holes, baffles disposed in front of the photometers to be spaced apart therefrom, an auxiliary light source disposed inside the integrating sphere, an auxiliary baffle disposed in front of the auxiliary light source, and a summing unit of output signals of the photometers under the illumination of a light source to be measured disposed in the central area inside the integrating sphere.