Provided is a filter for a pet water supply device with which adequate filtration performance can be reliably obtained. The present invention comprises: a water storage tank 1 for a pet water supply device, the water storage tank 1 being configured such that water drinking parts 31 are provided above the water storage tank 1, and the water supplied from the water storage tank 1 to the water drinking parts 31 returns to the water storage tank 1； and a filter 5 for the pet water supply device, the filter 5 being detachably provided between the water drinking parts 31, and being configured so that the water returning from the water drinking parts 31 to the water storage tank 1 is caused to pass from the upper-surface side to the lower-surface side of the filter 5. The present invention also comprises: a filter tray 6 in which an outer circumferential wall 62 is provided rising from a bottom wall 61 in which water passage holes 64 are formed； an interior filtration material 71 accommodated inside the filter tray 6； and an upper-surface cover filtration material 72 attached so as to cover upper-end openings in the filter tray 6. Partition walls 65 of the filter tray 6 are formed so that the lower side thereof, viewed from each chamber, is positioned inward of the upper side, and the outer circumferential wall 62 is formed such that the lower side thereof is positioned inward of the upper side.L'invention concerne un filtre pour un dispositif d'alimentation en eau pour animal domestique avec lequel une performance de filtration adéquate peut être obtenue de manière fiable. La présente invention comprend : un réservoir de stockage d'eau 1 pour un dispositif d'alimentation en eau pour animal domestique, le réservoir de stockage d'eau 1 étant configuré de telle sorte que des parties d'eau destinée à la consommation 31 soient disposées au-dessus du réservoir de stockage d'eau 1, et l'eau fournie par le réservoir de stockage d'eau 1 aux parties d'eau destinée à la consommation
