The invention provides a fluid measuring apparatus, which includes a collector, a sensing circuit, and an electrochromic device electrically connected to the sensing circuit. When the concentration of a fluid flowing through the collector and between the sensing circuit varies, the color of the electrochromic device changes accordingly. Further, the electrochromic device includes an electrochromic material, and the sensing circuit includes a first electrode and a second electrode, wherein the first and the second electrodes are disposed in the collector and the electrochromic material is disposed on the first electrode. When the concentration of an electrolytic solution flowing between the first electrode and the second electrode varies, the color of the electrochromic material changes accordingly.