1. A culture quality evaluation method, comprising: a first step of culturing a pluripotent stem cell under a predetermined culture condition and thereby creating a sample; a second step of imaging a proliferated cell colony in the sample and accordingly capturing an original image; a third step of dividing the original image into smaller images of a predetermined size and calculating standard deviations of pixel values of pixels contained in each one of the smaller images; and a fourth step of judging that the sample is an acceptable sample when a ratio of a number of the smaller images whose values of the standard deviations are within a predetermined range to a total number of the smaller images is equal to or smaller than a predetermined threshold value and judging that the sample is an unacceptable sample when the ratio is beyond the threshold value, wherein prior to the third step, an image of a pluripotent stem cell, an image of a feeder cell and an image of a differentiated cell differentiated from the pluripotent stem cell are acquired, a first sub step of calculating first standard deviations which are defined as the standard deviations of pixel values contained in each one of smaller images which are obtained by dividing the images, a second sub step of calculating an average value of the first standard deviations calculated on a plurality of smaller images and calculating a second standard deviation which is defined as a standard deviation of the first standard deviations, and a third sub step of identifying a central range which is defined as a range of first standard deviations within which the values of the first standard deviations are equal to or smaller than twice the second standard deviation about the average value are executed on the images while changing the size of the smaller images over multiple levels, and the size of the smaller images to use at the third step is determined as such a size with which the central range in the image of the differentiated cell does not overlap the central range in the image of the pluripotent cell or the central range in the image of the feeder cell under the condition that the smaller images have the same size wherein the steps are executed by one or more processors.