There is provided a white light source approximating sunlight and being capable of reproducing a subtle difference in sunlight which changes depending on times and locations, and provided a white light source system of a lighting system or the like. The white light source includes a light source unit. Light which is emitted from the light source unit is a chromaticity point on a CIE chromaticity diagram and has a correlated color temperature corresponding to a chromaticity point including a deviation of −0.005 or more to +0.005 or less with respect to a black body radiation locus, and satisfies a formula: −0.2≤[(P (λ)×V (λ))/(P (λmax1)×V (λmax1))−(B (λ)×V (λ))/(B (λmax2)×V (λmax2))]≤+0.2.