An object of the invention is to provide a bed which can surely detect the positional shift and heartbeat vibration of a bedded person while suppressing the increase of the cost and the degradation of the comfortability of a bed, and to provide a bed and an in-bed state detection method which can prevent the undesirable caught at the time of elevating the bed. In order to detect the shift of a bedded person, a ratio of intensities between output signals from first pressure sensitive sensor 21 and a second pressure sensitive sensor 22 each having a cable shape is obtained. These sensors are disposed along the lying direction at the both end sides of a bedding surface 15a on which a bedded person lies, respectively. When the ratio is in a range of a predetermined shift state set in advance, it is determined that the positional shift of a bedded person on the bedding surface 15a occurs. Further, a low-repulsion urethane layer is provided within a bed pad thereby to detect the heartbeat vibration. Furthermore, the elevational driving of the panel portion is controlled in accordance with the output form the pressure sensitive sensor disposed on a bed.