An absorbent article for a pet comprising: a top surface layer that is liquid permeable; a back surface layer (31, 32) that is liquid impermeable; and an absorbent core disposed between the top surface layer and the back surface layer, the absorbent article for a pet being configured in a rectangular shape with a first end portion and a second end portion facing each other and a pair of side portions facing each other orthogonal to the first end portion and the second end portion, and in a state in which the absorbent article for a pet is wrapped around a waist of a pet, the first end portion is positioned on a pet's body side and the second end portion is detachably attached to an outer face of the first end portion, characterised in that: the absorbent article for a pet further comprises: an elastic member (61, 62) that is disposed along a longitudinal direction of the absorbent article for a pet in a state of being extended; and a pair of side sheets (51, 52), which are respectively disposed on the top surface layer side of the pair of side portions; wherein a high stiffness portion, that is higher in stiffness than the second end portion, is formed in the first end portion; a belt-like tape member with a plurality of hook portions is attached to the outer face of the first end portion; the tape member is attached at a position away from an end edge of the first end portion by a predetermined distance, so as to extend in a width direction of the absorbent article for a pet; an inner face of the second end portion is constituted of a nonwoven fabric constituting at least one of the top surface layer and the side sheet; the second end portion is not provided with a loop member; and the inner face of the second end portion is constituted of a nonwoven fabric with which the plurality of hooks is engageable. the absorbent article for a pet further comprises: an elastic member (61, 62) that is disposed along a longitudinal direction of the absorbent article for a pet in a state of being extended; and a pair of side sheets (51, 52), which are respectively disposed on the top surface layer side of the pair of side portions; wherein a high stiffness portion, that is higher in stiffness than the second end portion, is formed in the first end portion; a belt-like tape member with a plurality of hook portions is attached to the outer face of the first end portion; the tape member is attached at a position away from an end edge of the first end portion by a predetermined distance, so as to extend in a width direction of the absorbent article for a pet; an inner face of the second end portion is constituted of a nonwoven fabric constituting at least one of the top surface layer and the side sheet; the second end portion is not provided with a loop member; and the inner face of the second end portion is constituted of a nonwoven fabric with which the plurality of hooks is engageable. an elastic member (61, 62) that is disposed along a longitudinal direction of the absorbent article for a pet in a state of being extended; and a pair of side sheets (51, 52), which are respectively disposed on the top surface layer side of the pair of side portions; wherein a high stiffness portion, that is higher in stiffness than the second end portion, is formed in the first end portion; a belt-like tape member with a plurality of hook portions is attached to the outer face of the first end portion; the tape member is attached at a position away from an end edge of the first end portion by a predetermined distance, so as to extend in a width direction of the absorbent article for a pet; an inner face of the second end portion is constituted of a nonwoven fabric constituting at least one of the top surface layer and the side sheet; the second end portion is not provided with a loop member; and the inner face of the second end portion is constituted of a nonwoven fabric with which the plurality of hooks is engageable.