Continuous business process improvement is a well-known strategy referred to as the “Japanese approach” to industrial production. Nowadays, it presents one of the basic requirements set by the ISO 9004:2000 standard. A new fuzzy model based on the Ishikawa diagram is proposed, whereby the rank of business losses of the main process at the manufacturing company level is determined, respecting the values of identified causes that lead to the formation of business losses, as well as their relative importance. In this article, it is assumed that the relative importance and values of causes are determined by descriptive linguistic expressions. The linguistic expressions are obtained by the fuzzy rating of a management team. The proposed algorithm determines the business losses with the highest possibility of occurrence and calculates the degrees of beliefs that some business losses are more likely to happen than the others. Real-life industrial data on small and medium companies operating in central Serbia and numerical examples are given to illustrate the method.