A device that adds and removes a load of a built-in weight to and from a load measuring mechanism of a weighing apparatus built-in weight latched in a weight holder that performs a lifting and lowering operation to a fixed portion. During calibration, gas is supplied from a gas supply and exhaust portion to a bag to increase volume of the air bag. At this point, the weight holder is lowered against the repulsive force of a coil spring, and the built-in weight is latched in the load receiver, thereby performing the calibration. After the calibration, an electromagnetic valve is opened to exhaust the gas from the bag. As a result, the weight holder is lifted by the repulsive force of the coil spring, and the weighing apparatus enters a usual weighing mode.