Provided are a test water supply device and a water-flowing fish testing device capable of maintaining the accuracy of measuring dilution water and improving the supply speed of the dilution water. A dilution water supply means (20) includes: a dilution water measuring vessel (24) for measuring dilution water to be supplied to a test water supply means (10) a first dilution water supply means (30) for supplying the dilution water to the dilution water measuring vessel (24) a second dilution water supply means (40) for supplying the dilution water to the dilution water measuring vessel (24) in an amount smaller than that supplied from the first dilution water supply means (30) per unit time and a control means for controlling the first dilution water supply means (30) and the second dilution water supply means (40). The control means causes at least the first dilution water supply means (30) to supply the dilution water to the dilution water measuring vessel (24) until a predetermined condition is satisfied. After the predetermined condition is satisfied, the control means causes only the second dilution water supply means (40) to supply the dilution water to the dilution water measuring vessel (24). As a result, a predetermined amount of the dilution water is supplied to the dilution water measuring vessel (24).Linvention concerne un dispositif dalimentation en eau dessai et un dispositif dessai à circulation deau pour poisson, capables de maintenir la précision de mesure de leau de dilution et daméliorer la vitesse dalimentation de leau de dilution. Un moyen (20) dalimentation en eau de dilution comprend : un récipient (24) de mesure pour eau de dilution servant à mesurer de leau de dilution destinée à être fournie à un moyen (10) dalimentation en eau dessai un premier moyen (30) dalimentation en eau de dilution servant à fournir leau de dilution au récipient (24) de mesure pour eau de dilution un deuxième moyen (40) dalimentation en eau de dilution servant à fou
