A posture estimation device, which is able to estimate the posture of a humanoid articulated body with high precision, has: a head estimation unit (120) that estimates the position of a person's head from image information for an image that contains a person; a foot estimation unit (130) that, from the image information, estimates the position of the person's foot for which the sole of the foot is parallel to the floor surface; and a posture estimation unit (140) that estimates the posture of the person on the basis of the relative positional relationship between the estimated head position and the estimated foot position. For example, the posture estimation unit (140) estimates the side on which the foot is located, with respect to the head, as the front side of the person.