To obtain a system for detecting defective print in which a decision can be made accurately which color of ink jet printer is attributable to defective print when an ink jet color printer is used.

The system (3) for detecting defective print of color print information comprises an imaging means (3a) for detecting color print information as a color image, and means (3b) for detecting defective print of color print information based on the detection results of the imaging means. The detecting means detects the print density information of each color based on the detection results of the imaging means.