Abstract: A fluid flow measurement system including a sheet-shaped light emitting device that emits a sheet-shaped light into a flow field of a fluid containing particles; a CMOS image sensor that captures an image on a sheet emitted by the light-emitting device and that can convert the image signal into digital data; a timing controller that synchronizes the light-emitting device and the CMOS image sensor; and an image processor that compares and analyzes luminance pattern distributions of images on the sheet captured by the CMOS image sensor at various times, for measuring movement direction and movement amount of the particles. As needed, a transmission line is used or the imaging interval is shortened by using two CMOS image sensors and a beam splitter. Thereby, PIV can be used when the light amount is insufficient, the system is in a radiation environment, or flow speed is high.