A fluid measuring apparatus is provided with: an irradiating device configured to irradiate a fluid with light； a light receiving device configured to receive light scattered by the fluid； a detecting device configured to detect a backflow of the fluid on the basis of a received light signal of the light receiving device； and a calculating device configured to calculate estimated fluid information indicating a flow volume or a flow velocity of the fluid, on the basis of a detection result of the detecting device and the received light signal of the light receiving device. By this, even if the backflow temporarily occurs in the fluid, the speed of the fluid can be accurately measured.
