The present invention relates to a pet litter box which prevents the surrounding environment from becoming contaminated due to excrement of a pet being exposed to the outside, comprises a main body, a cover, a door, and a multifunctional filter unit which are separably coupled, so as to easily prevent the generation of odor from the excrement of a pet and bacterial growth, and can prevent unnecessary expense increases while achieving usage convenience. The pet litter box comprises: a main body having a box shape of which an upper portion is open； a cover which is formed to be coupled to the main body so as to cover the open portion of the main body, and which is provided with a pet entrance at the front thereof, open windows on opposing left and right sides thereof to communicate with the outside, and a vent window in an upper portion thereof which forms a connecting part of the open windows, wherein a door is coupled to the pet entrance so as to be openable and closable, and a multifunctional filter unit, which has antibacterial, and odor adsorption and elimination functions, is detachably coupled to the open windows and the vent window.
