To provide a flow rate integrating meter which can extremely simply integrated and measure an accurate undiluted solution per unit time and is further suitably provided in water processing facilities disposed in many positions since it is lower priced than a conventional flow meter, and its flow rate integrating method.

In a flow rate integrating meter 1 provided in an undiluted solution supply duct 6 on a discharge side of an undiluted solution supply pump for supplying an undiluted solution at a fixed amount, this simple flow rate integrating meter comprises an air bent 2 provided so as to bypass in a vertical downward duct part of the undiluted solution supply duct 6 and vertically provided containing a bent closing valve 4; a transparent measuring cylinder 3 vertically provided on a downward side of a bypass part; and a closing valve 5 provided on a downstream side of the measuring cylinder 3, and its integrating method is indicated.