A flow measurement method for optical measurement of a volume flow of a fluid in a closed cross-section, and a flow measurement device for this purpose, has at least one light source and at least one sensor unit. Particles present in the fluid are detected within a measurement plane by the sensor unit. At least one measurement plane and the particles present therein are illuminated with the light source. The sensor unit is provided with at least two or with a plurality of individual detectors with which sensor signals are outputted. A computing unit is connected downstream of the sensor unit, with which the sensor signals are processed in real time by integrating and weighting the individual signals of the individual detectors using a spatial-filtering technique and outputted as an output signal.