A flow rate measuring device comprising: a flow rate measurement unit for measuring the flow rate of fluid flowing through a flow passage at constant time intervals; a calculation unit for calculating difference values of the flow rate measured by the flow rate measurement unit at constant time intervals, wherein a difference value equals the difference between a first flow rate Q(n) and a second flow rate Q(n - 1), wherein the second flow rate Q(n - 1) is measured at a last time; a flow rate classification table in which the classifications of a plurality of difference values depending on the magnitudes of the difference values are associated with codes representing the classifications; a difference value conversion unit for converting the difference values calculated by the calculation unit into codes on the basis of the flow rate classification table, wherein a code represents a number; and an appliance identification unit for performing appliance identification; characterized by: an appliance feature extraction unit for generating an appliance feature code string indicating the feature of an appliance from the codes obtained at constant time intervals by the difference value conversion unit; wherein the appliance identification unit is configured to perform appliance identification by comparing the appliance feature code string with an appliance inherent feature code string indicating the feature code string inherent in each appliance, said appliance feature extraction unit is configured to generate said appliance feature code string in the following way: in the case that the last code of the codes obtained by the difference value conversion unit is larger than the second last code and the last code is larger than the current code or in the case that the last code is smaller than the second last code and the last code is smaller than the current code, the appliance feature extraction unit stores the current code in the appliance feature code string; and in the other cases, the extraction unit overwrites the current code on the last code stored in the appliance feature code string. a flow rate measurement unit for measuring the flow rate of fluid flowing through a flow passage at constant time intervals; a calculation unit for calculating difference values of the flow rate measured by the flow rate measurement unit at constant time intervals, wherein a difference value equals the difference between a first flow rate Q(n) and a second flow rate Q(n - 1), wherein the second flow rate Q(n - 1) is measured at a last time; a flow rate classification table in which the classifications of a plurality of difference values depending on the magnitudes of the difference values are associated with codes representing the classifications; a difference value conversion unit for converting the difference values calculated by the calculation unit into codes on the basis of the flow rate classification table, wherein a code represents a number; and an appliance identification unit for performing appliance identification; an appliance feature extraction unit for generating an appliance feature code string indicating the feature of an appliance from the codes obtained at constant time intervals by the difference value conversion unit; wherein the appliance identification unit is configured to perform appliance identification by comparing the appliance feature code string with an appliance inherent feature code string indicating the feature code string inherent in each appliance, said appliance feature extraction unit is configured to generate said appliance feature code string in the following way: in the case that the last code of the codes obtained by the difference value conversion unit is larger than the second last code and the last code is larger than the current code or in the case that the last code is smaller than the second last code and the last code is smaller than the current code, the appliance feature extraction unit stores the current code in the appliance feature code string; and in the other cases, the extraction unit overwrites the current code on the last code stored in the appliance feature code string. in the case that the last code of the codes obtained by the difference value conversion unit is larger than the second last code and the last code is larger than the current code or in the case that the last code is smaller than the second last code and the last code is smaller than the current code, the appliance feature extraction unit stores the current code in the appliance feature code string; and in the other cases, the extraction unit overwrites the current code on the last code stored in the appliance feature code string.