A defect detection system includes a data acquiring section that acquires time series data of device parameter of each manufacturing device including an exposure device, and information on defect distribution in an area with a size smaller than a chip area size, a pattern classifying section that assembles the information on the defect distribution in units of shot or chip areas, and classifies the distributions to a defect pattern, a feature quantity calculating section that processes the time series data and calculates a feature quantity, a significant difference test section that calculates occurrence frequency distributions of the shot or chip area wherein the defect pattern to the feature quantity exists and does not exist, respectively, and determines the presence/absence of significant difference between the frequency distributions, and a defect detecting section that detects the device parameter corresponding to the feature quantity as the cause of defect of the defect pattern.