1. A combinatorial weighing method for performing a combinatorial calculation based on output data from a plurality of weighing machines and for selecting a combination of weight data, corresponding to the output data, indicative of a total combined weight equal or closest to a target value within a preset range, comprising the steps of: (a) repeatedly reading output data from each of the weighing machines and storing the output data as plural data items for the respective weighing machines in a weighing cycle shorter than a combinatorial calculation cycle and preset according to the weighing machines supplied with articles to be weighed; (b) obtaining the mean value of the plural data items stored for the respective weighing machines, and updating a preceding mean value with the current mean value; (c) determining, for each weighing machine, whether the weighing machine is in a stable state based on a comparison between the preceding mean value and the current mean value; and (d) performing a combinatorial calculation upon weight data corresponding to the output data from each weighing machine sensed to be in a stable state, in a next combinatorial calculation cycle.