This study was written to assess microbilogical quality by passage of time and holding method after making foods, by means of evaluating time, temperature and microbiological quality during vairous phases in product flow of hard-boiled mackerel served by an industry feeding operation for 500 persons a day, measuring pH & Aw and analyzing factors affecting nicrobiological growth conditions. The results were as fallows: 1. According to phases in product flow of hard-boiled mackerel, it showed 4.9 hours of mean of needed time, $27.5^{circ}C$ of room temperature, 4.8~5.7 of pH value and 0.95~0.98 of Aw. these conditions were suitable for microbiological growth, and the phases with potential hygienic danger were pre-preparation and assembly & service. 2. As for holding methods and passage of time, holding as steam table was more effective than holding at room temperature as time past. 3. Food poisoning bacteria were not dectected from phases in product flow of hard-boiled mackerel.