A flow rate measurement device includes a flow rate measurer to measure a fluid flow rate at regular time intervals, a period setting unit, an arithmetic unit to calculate first average flow rates and amounts of change each between the average flow rates in sequence, and second average flow rates and amounts of change each between the average flow rates in sequence, and a fuel cell determinator to determine whether a fuel cell is in operation. The fuel cell determinator determines that a fuel cell is in operation when an increment of the second average flow rate repeats for first predetermined successive times, an increment of the first average flow rate repeats for second predetermined times or more in each of the second periods, and an increment of the first average flow rate not greater than or equal to a third predetermined flow rate in each of the second periods.