To provide a washing verification method and a washing verification system, which enable a high-precision verification of a normal washing treatment in a tank.

The washing verification method comprises a step of detecting a cleaning liquid jetted out toward an inner surface of the tank 1 by a non-contact detecting means 2 arranged outside the tank 1, and a step of judging whether or not the washing treatment inside the tank 1 is carried out normally from a detecting signal output from the detecting means 2. Further, the washing verification system is provided with a light transmission portion 3 making light penetrate, provided on a part of the tank 1, an irradiated part 2a irradiating the cleaning liquid jetted out toward the inner surface of the tank 1 with the light through the light transmission portion 3, a light receiving element 2b detecting the light returning from inside of the tank 1 through the light transmission portion 2a, and a controller 5 judging whether or not the washing treatment inside the tank 1 is carried out normally from the light quantity change detected by the light receiving element 2b.