A flow rate measurement device improves the flow rate measurement accuracy without increasing the size of the metering tank. The flow rate measurement device includes a metering tank having a supply port at its upper portion and a discharge port at its lower portion, an on-off valve that opens and closes a flow channel inside the metering tank, a weight measurement unit that measures a weight of the metering tank, and flow rate computing unit that supplies powders and/or grains continuously from the supply port to the metering tank, computes a flow rate of the powders and/or grains multiple times in a temporally-overlapped state on the basis of the weight of the metering tank measured by the weight measurement unit in a state where the on-off valve is closed, and computes an average flow rate of the powders and/or grains on the basis of the flow rate computed multiple times.