A pet litter box includes a litter container for storing liquid-passing litter and a liquid-absorbing sheet tray for holding a liquid-absorbing sheet. The front-back direction of the liquid-absorbing sheet can be changed without removing the liquid-absorbing sheet from the tray. The pet litter box includes a litter box main body having an opening from which pets enter. The litter box main body includes a litter container for storing liquid-passing litter formed of plural of granular materials provided therein, a liquid-absorbing sheet placed below the litter container for absorbing the liquid passing through the litter, and a liquid-absorbing sheet tray for holding the liquid-absorbing sheet. The liquid absorbing sheet tray can be withdrawn and removed from the front of the litter box main body and reversible in the front-back direction.