Provided is a flow rate measuring device wherein operation is simplified by a configuration which extracts the features of an appliance, and accuracy of appliance discrimination is enhanced by reducing the quantity of memory required for operation and absorbing variation caused by manual operation or ignition condition. A flow measuring device comprises a difference value conversion means (112) for converting the difference value of flow rate measured by an ultrasonic flowmeter (104) at a fixed time interval into a code, an appliance feature extraction means (214) for creating an appliance feature code string indicating the feature of the appliance by performing comparison, determination, deletion of a code, or the like, by use of the code at the second time before last, the code at the time before last, the code at the last time and the code at the current time from codes obtained every predetermined time, and a discrimination means (116) for discriminating an appliance by comparing the appliance feature code string and an appliance specific feature code string indicating the specific feature code of the appliance.