1. An image analysis method of a scanning type optical microscope to analyze a scanned image acquired by detecting light from a measurement point in a sample mixed with molecules of different sizes and scanning of the measurement point to be detected, comprising: an image acquiring step of acquiring, in time-series, scanned images of frames comprising pixels in which pixel data of the respective scanned images are acquired in time-series; an analysis area setting step of setting analysis areas to the scanned images; a classification value calculating step of calculating a classification value of each of the analysis areas; a classifying step of classifying the scanned images into two or more groups on the basis of magnitude of change of the classification value; an average image calculating step of calculating an average image of the analysis area of every group; a new image calculating step of subtracting the average image from each scanned image of the analysis area of every group to calculate a new image of the analysis area; and a calculation step of calculating a correlation value by raster-image correlation spectroscopy on the basis of the new images of every group.