To provide a quality judging system capable of easily changing judgement logic by the change of components by expressing data to be a base for the preparation of judgement logic as components and preparing the judgement logic by the combination of these components.

The system is provided with a measuring part 1 selecting an optional product from continuously manufactured products and measuring the quality of the selected product, a data set part 2 for expressing retrieving ranges and retrieval invalidating conditions as plural sorts of components, a judgement logic preparing part 3 capable of preparing judgement logic by combining optional components out of plural sorts of retrieving ranges and retrieving conditions expressed as components by the data set part 2 and changing the combinations, and a quality judging part 4 for processing the measurement data obtained by the measuring part 1 in accordance with the judgement logic prepared by the preparing part 3 and judging the quality of a product.