To provide the pressure-measuring device of a vacuum device that accurately measures pressure in the vacuum device with a high response property, and at the same time freely sets a pressure-measuring range in a vacuum region.

When pressure is measured, a booster pump 50 for measuring pressure being connected to an extremely high-vacuum container 10 via an intake port is actuated, gas in the extremely high-vacuum container 10 circulates in the order of the booster pump 50 for measuring pressure, a fine adjustment flow-rate variable valve 52, and the extremely high-vacuum container 10, the gas in the extremely high-vacuum container 10 is compressed to an arbitrary pressure range in the pump 50 while being introduced to pressure gauges 51a and 51b, the entire pressure and the partial pressure of each gas are measured, the measured value is divided by the compression ratio of each of known gas of the booster pump 50 for measuring pressure, and vacuum pressure (the entire pressure and the partial pressure) is obtained. At this time, the opening of the fine adjustment flow-rate variable valve 52 is changed and a pressure range to be measured is arbitrarily set.