Vegetables are vital sources from which Vitamin C is supplied. According to the National Statistics, the amount of daily per head average intake of Vitamin C is about 74mg calculated on raw material of which about 85% is taken from vegetables. Since Vitamin C is easily affected by heating or oxidation in cooking, the loss is not a little. Consequently, it is presumed that real amount of intake will be far below than basic amount. It is therefore very important prerequisite to find out how much percent of loss there will be in case of cooking in order to decide actual amount of intake for proper nutrition by people. When surveyed sundry records on the loss of C in the process of cooking, they state their experiments of how to chop materials, degrees and duration of heating to find the results or a certain material simply cooked to get the result for the test. These experiments abound in the records. But when we see especially in farming districts the way of cooking is very simple and most vegetables are used in soup and some are boiled, heated for quite a while in both cases so a great deal of Vitamin C is naturally lost. It is hard to find any research made systematically to find this loss. Therefore, the researcher making experiments by way of cooking done in ordinary homes checked the amount of the loss of C in food materials together in making nutritive research tried to find out real amount of C intake based on apparent amount of C intake calculated from the raw materials. In this paper, however, only the result of experiments made consumers' homes is stated as the object of study.