A cancer analysis system includes, so as to perform an efficient image analysis in a cancer screening test using nematodes: a light source unit that irradiates a plate on which nematodes and a urine sample are plotted, from below; a photographing unit that takes an image of the plate irradiated by the light source unit; and an analyzer that analyzes the image taken by the photographing unit. The analyzer: couples a prescribed number of pixels in the image into a larger number of pixels thereof; and performs a chemotaxis assay of the nematodes based on a time variation of information on a luminous center of gravity of the image.