A pressure-adjusting apparatus for vise including a bolt and a pressure-adjusting element is provided. The bolt having a plurality of positioning holes is adapted for connecting to a vise. The pressure-adjusting element is sleeved onto the bolt movably. The distance between the pressure-adjusting element and the vise can be changed by moving the pressure-adjusting element so as to adjust the clamping force of the vise. A positioning member of the pressure-adjusting element is stocked in one of the positioning holes when the pressure-adjusting element is moving so that the pressure-adjusting element can be fixed at a preset location. Thus, the pressure-adjusting apparatus for vise of the present invention is more convenient for pressure adjustment.