An object estimation device includes an acquisition unit and an estimation unit. The acquisition unit acquires a space image including an object present in a space. The estimation unit estimates image region data on the basis of a portion or all of the space image including the object. The image region data indicates a location of the object in the space image. On the condition that the object included in the space image acquired by the acquisition unit is included in an oblique posture, the estimation unit estimates an image region widened from an image region of the object included in the oblique posture in the space image, as the image region data.