In a posture detection device and a posture detection method of the present invention, an image of a prescribed detection area is acquired by an image acquisition unit, a head portion is extracted from the acquired image of the detection area, a prescribed parameter for the extracted head portion is determined, and whether a prescribed posture is taken is determined on the basis of the determined parameter. Therefore, in the posture detection device and posture detection method of the present invention, the posture of a monitored subject can be determined more precisely with a simpler configuration.
