Defects of substrates are inspected when executing a job in which a treatment recipe for substrates and the substrates being treatment objects are designated to perform predetermined treatments on the substrates. An imaging step successively images substrates. A first determination step decomposes, in order from the substrate as head of the job, a planar distribution of pixel values in a substrate image captured at the imaging step into pixel value distribution components using a Zernike polynomial, calculates Zernike coefficients of the pixel value distribution components corresponding to defects to be detected, and determines presence or absence of a defect based on the calculated Zernike coefficients. A second determination step determines, from predetermined timing after one or more substrates is determined to have no defect at the first determination step, presence or absence of a defect based on the substrate image determined to have no defect at the first determination step.