Abstract: An apparatus for continuously taking off a thermoplastic synthetic resin sheet foamed by a vertical foaming furnace which has a rail fixedly disposed horizontally, two bodies mounted obliquely at the same angle in a linear symmetrical manner with respect to a vertical line and moving in parallel along the rail, a driver for driving the bodies, two holding roll rows having a plurality of holding rolls disposed in a zigzag manner along the longitudinal direction of the body, a pair of supports respectively wound on the holding rolls, and sensors having optical fiber sensors electrically connected to the driver and provided at each of the upper ends of the bodies. The interval of the two bodies is defined to be narrow at its top and wider toward the lower interval. The degree of the width of the foamed sheet is determined by the angle. The sensor includes two casing halves. One casing half contains a light emitting unit of the optical fiber sensor.