A weight estimation device comprising: an image acquisition unit that acquires an image of an animal; an information generation unit that is capable of generating estimation information indicating a shape of the animal from the image; an information storage unit that stores therein carcass model information indicating a shape of carcasses; and a weight estimation unit that estimates a weight of carcasses of the animal on a basis of the estimation information and the carcass model information, wherein the information generation unit is, even when an image in which the animal is imaged from an obliquely upward direction as viewed from the animal is acquired, capable of generating the estimation information indicating a shape of one portion of the animal from the image, and the weight estimation unit estimates the weight of carcasses of the animal on a basis of a shape of carcasses indicated by the carcass model information having been transformed according to a shape of one portion of the animal indicated by the estimation information, characterized in that weight estimation device further comprises: a shape identification unit that identifies a shape of a spine of the animal from the image of the animal; and a half-body selection unit that selects, as a specified half body, either one of a right side of a body and a left side of the body, respectively positioned on a right side and a left side from the spine as viewed from the animal, wherein the information generation unit estimates a shape of a half body not selected as the specified half body from a shape of the specified half body and is, upon acquisition of the image, capable of automatically generating information indicating a shape of the animal generated by combining the estimated shape of the half body and the shape of the specified half body as the estimation information. an image acquisition unit that acquires an image of an animal; an information generation unit that is capable of generating estimation information indicating a shape of the animal from the image; an information storage unit that stores therein carcass model information indicating a shape of carcasses; and a weight estimation unit that estimates a weight of carcasses of the animal on a basis of the estimation information and the carcass model information, wherein the information generation unit is, even when an image in which the animal is imaged from an obliquely upward direction as viewed from the animal is acquired, capable of generating the estimation information indicating a shape of one portion of the animal from the image, and the weight estimation unit estimates the weight of carcasses of the animal on a basis of a shape of carcasses indicated by the carcass model information having been transformed according to a shape of one portion of the animal indicated by the estimation information, characterized in that weight estimation device further comprises: a shape identification unit that identifies a shape of a spine of the animal from the image of the animal; and a half-body selection unit that selects, as a specified half body, either one of a right side of a body and a left side of the body, respectively positioned on a right side and a left side from the spine as viewed from the animal, wherein the information generation unit estimates a shape of a half body not selected as the specified half body from a shape of the specified half body and is, upon acquisition of the image, capable of automatically generating information indicating a shape of the animal generated by combining the estimated shape of the half body and the shape of the specified half body as the estimation information. a shape identification unit that identifies a shape of a spine of the animal from the image of the animal; and a half-body selection unit that selects, as a specified half body, either one of a right side of a body and a left side of the body, respectively positioned on a right side and a left side from the spine as viewed from the animal, wherein the information generation unit estimates a shape of a half body not selected as the specified half body from a shape of the specified half body and is, upon acquisition of the image, capable of automatically generating information indicating a shape of the animal generated by combining the estimated shape of the half body and the shape of the specified half body as the estimation information.