A system for fabricating a corrugated board sheet comprising: running-state information obtaining means for obtaining running state information concerning a current running state of a corrugated-board fabrication machine; production-state information obtaining means for obtaining production state information concerning a production state in the corrugated-board fabrication machine; control variable calculating means for calculating a control variable of each of control factors used to control the corrugated-board fabrication machine based on the running state information obtained by said running-state information obtaining means and the production state information obtained by said production-state information obtaining means; quality information detecting means (7, 8D) for detecting that the corrugated board sheet fabricated by the corrugated-board fabrication machine satisfies a predetermined quality; optimum running-condition information retaining means for retaining, if said quality information detecting means (7, 8D) detects that the corrugated board sheet satisfies the predetermined quality, a portion of the running state information obtained by said running-state information obtaining means which portion is associated with a particular control factor that affects the predetermined quality, so that the portion of the running-state information serves as optimum running-condition information corresponding to the production state at a time point of a detection by said quality information detecting means (7, 8D); and control means for preferentially controlling, if the optimum running condition information retained in said optimum running-condition information retaining means is corresponding to a current production state, the particular control factor so as to become in the optimum running condition. running-state information obtaining means for obtaining running state information concerning a current running state of a corrugated-board fabrication machine; production-state information obtaining means for obtaining production state information concerning a production state in the corrugated-board fabrication machine; control variable calculating means for calculating a control variable of each of control factors used to control the corrugated-board fabrication machine based on the running state information obtained by said running-state information obtaining means and the production state information obtained by said production-state information obtaining means; quality information detecting means (7, 8D) for detecting that the corrugated board sheet fabricated by the corrugated-board fabrication machine satisfies a predetermined quality; optimum running-condition information retaining means for retaining, if said quality information detecting means (7, 8D) detects that the corrugated board sheet satisfies the predetermined quality, a portion of the running state information obtained by said running-state information obtaining means which portion is associated with a particular control factor that affects the predetermined quality, so that the portion of the running-state information serves as optimum running-condition information corresponding to the production state at a time point of a detection by said quality information detecting means (7, 8D); and control means for preferentially controlling, if the optimum running condition information retained in said optimum running-condition information retaining means is corresponding to a current production state, the particular control factor so as to become in the optimum running condition.