A posture determination device for determining a user's posture including: a plurality of pressure detection parts disposed in a matrix arrangement on a human body support surface of bedding； a pressure sensing center calculation member to calculate a pressure sensing center of the pressure detection parts based on output values of the pressure detection parts； a determination area setting member to set at least one determination area around the calculated pressure sensing center； and a posture determination member to determine the posture based on distribution condition of the output values of the pressure detection parts within the determination area.
