Abstract: A pillow type pressure detector having a base board on the front surface of which a load cell type load sensor is mounted; a holder cover which is so provided as to be spaced a predetermined distance from the base board; a flat-plate-shaped load transmitting board and a flat-plate-shaped retaining board positioned between the base board and the holder cover; a pillow type pressure reaction jig positioned between the load transmitting board and the retaining board; and a pillow holding member for clamping predetermined portions of the pressure reaction jig mounted over the base board and the holder cover. There are provided a mechanism for simultaneously swinging the load transmitting board and the retaining board relative to the base board, a mechanism elastically supporting the pillow holding member on the side of the base board and/or a thin-plate-shaped depressing member provided over the surface of the load sensor for fixedly secure the load sensor to the base.