The present invention provides a method of determining a structure of an antireflection coating formed on a substrate as an exposure target of an exposure apparatus, the method comprising steps of calculating, an intensity distribution of light diffracted by an original, based on information of an effective light source formed on a pupil plane of a projection optical system, and information of an original pattern, extracting diffracted light having an intensity of not less than a threshold from the intensity distribution calculated in the calculating step, and determining the structure of the antireflection coating, formed on the substrate, such that a reflectance of the antireflection coating falls within a target range when an incident angle of the diffracted light, which has the intensity of not less than the threshold and is extracted in the extracting step, on the antireflection coating formed on the substrate is an input.