Using fabrication-time variation predicting means that predicts this fact, the variation is predicted beforehand at the design stage prior to fabrication and is stored in variation prediction storage means. Rather than measuring a delay, testing an operation is performed (by a pass/fail determination) by actual-speed logic operation testing means for checking, after fabrication, whether a flip-flop (FF) operates at a specified operation frequency. As a result, the variation is estimated using the non-operation flip-flop (FF) information and the predicted value of the variation from the fabrication-time variation predicting means, and a delay value which corrects for the variation is inserted into a fabricated semiconductor integrated circuit by post-fabrication delay insertion position/value determining means using the variation value that has been estimated.