An acquiring unit of a structured illuminating microscopy apparatus acquires at least two modulated images having the same wave number vector and the different phases; and a calculating unit of the structured illuminating microscopy apparatus, in a spatial frequency spectrum of each of at least the two modulated images acquired by the acquiring unit, separates a 0th-order modulating component and ±first-order modulating components of observational light fluxes superimposed on arbitrary two observation points based on at least four observation values regarding the two observation points which are mutually displaced by an amount of the wave number vector.