A disposable diaper for pets, comprising: a back-side waist area, an abdomen-side waist area and a crotch area between the back-side waist area and the abdomen-side waist area, a diaper longitudinal direction in which the back-side waist area, the crotch area and the abdomen-side waist area contiguously extend when the disposable diaper is not worn by a pet, and a diaper transverse direction crossing the diaper longitudinal direction, both ends in the diaper longitudinal direction (110A, 130A), and both ends in the diaper transverse direction, a tail insertion opening formed in a prescribed region in the diaper longitudinal direction, an absorbent core formed on one side of the tail insertion opening in the diaper longitudinal direction and disposed in a prescribed region extending over the crotch area and the abdomen-side waist area, an absorbent-core non-arrangement region in which the absorbent core is not disposed, a fastening part having a prescribed length and provided on the abdomen-side waist area, a fastening region provided in the back-side waist area and configured to receive the fastening part, a leg stretchable elastic member which is disposed in a stretched state in a prescribed region extending in the diaper longitudinal direction between the absorbent core and each of the ends in the diaper transverse direction, leg gathers formed by contraction of the leg stretchable elastic member, and a waist stretchable elastic member disposed in a stretched state in the absorbent-core non-arrangement region in the diaper transverse direction, wherein: when the disposable diaper is put on the pet, the crotch area and the abdomen-side waist area cover a crotch and an abdomen of the pet, while the back-side waist area is closely fitted to a back of the pet, and the fastening part is fastened to the fastening region, the weight of the absorbent core after excretion is received in the longitudinal direction of the fastening part while the disposable diaper is worn by the pet, a contraction force intersecting region in which contraction force of the leg stretchable elastic member and contraction force of the waist stretchable elastic member intersect with each other is formed, characterized in that: the leg stretchable elastic member and the waist stretchable elastic member are overlapped with each other. a back-side waist area, an abdomen-side waist area and a crotch area between the back-side waist area and the abdomen-side waist area, a diaper longitudinal direction in which the back-side waist area, the crotch area and the abdomen-side waist area contiguously extend when the disposable diaper is not worn by a pet, and a diaper transverse direction crossing the diaper longitudinal direction, both ends in the diaper longitudinal direction (110A, 130A), and both ends in the diaper transverse direction, a tail insertion opening formed in a prescribed region in the diaper longitudinal direction, an absorbent core formed on one side of the tail insertion opening in the diaper longitudinal direction and disposed in a prescribed region extending over the crotch area and the abdomen-side waist area, an absorbent-core non-arrangement region in which the absorbent core is not disposed, a fastening part having a prescribed length and provided on the abdomen-side waist area, a fastening region provided in the back-side waist area and configured to receive the fastening part, a leg stretchable elastic member which is disposed in a stretched state in a prescribed region extending in the diaper longitudinal direction between the absorbent core and each of the ends in the diaper transverse direction, leg gathers formed by contraction of the leg stretchable elastic member, and a waist stretchable elastic member disposed in a stretched state in the absorbent-core non-arrangement region in the diaper transverse direction, wherein: when the disposable diaper is put on the pet, the crotch area and the abdomen-side waist area cover a crotch and an abdomen of the pet, while the back-side waist area is closely fitted to a back of the pet, and the fastening part is fastened to the fastening region, the weight of the absorbent core after excretion is received in the longitudinal direction of the fastening part while the disposable diaper is worn by the pet, a contraction force intersecting region in which contraction force of the leg stretchable elastic member and contraction force of the waist stretchable elastic member intersect with each other is formed, characterized in that: the leg stretchable elastic member and the waist stretchable elastic member are overlapped with each other. when the disposable diaper is put on the pet, the crotch area and the abdomen-side waist area cover a crotch and an abdomen of the pet, while the back-side waist area is closely fitted to a back of the pet, and the fastening part is fastened to the fastening region, the weight of the absorbent core after excretion is received in the longitudinal direction of the fastening part while the disposable diaper is worn by the pet, a contraction force intersecting region in which contraction force of the leg stretchable elastic member and contraction force of the waist stretchable elastic member intersect with each other is formed, characterized in that: the leg stretchable elastic member and the waist stretchable elastic member are overlapped with each other.