A load weighting control apparatus that suppresses deterioration of a controlled object due to impacts or the like during control, and for which energy usage costs required for control are markedly reduced, and that has a simple structure and therefore inexpensive manufacturing costs and running costs. The apparatus includes a main vacuum cylinder provided with a cylinder tube, end walls, an air vent that passes through one end wall, a valve that is provided in the air vent and serves to open/tightly close the atmosphere inside of the cylinder tube to the outside, a piston that slides back and forth within the cylinder tube, and a piston rod that is linked to the piston and passes through the other end wall and an auxiliary vacuum cylinder that includes a slacking portion where a piston rod produces slackness in the main vacuum cylinder.