A vacuum-exhaust device connected to a vacuum container and adapted to evacuate the vacuum container, the vacuum-exhaust device comprising: an oil-rotary vacuum pump connected to the vacuum container and adapted to evacuate the vacuum container; a pair of on-off valves (121, 122) provided in series between the vacuum container and the oil-rotary vacuum pump; a vacuometer positioned between the pair of on-off valves (121, 122) and adapted to measure a vacuum degree; and a controller that controls the pair of on-off valves (121, 122) to be opened or closed based on the vacuum degree measured by the vacuometer characterized in that the controller is configured to control a vacuum-exhaust operation so that: a first on-off valve provided adjacent to the vacuum container, when the oil-rotary vacuum pump is driven, is opened for a predetermined time so as to store container vacuum-degree data about a vacuum degree of the vacuum container measured by the vacuometer; the first on-off valve is closed, and a second on-off valve provided adjacent to the oil-rotary vacuum pump is subsequently opened so as to obtain pump vacuum-degree data about a vacuum degree in the vicinity of the oil-rotary vacuum pump measured by the vacuometer; and the pair of on-off valves (121, 122) are opened when the controller recognizes that the vacuum degree in the vicinity of the oil-rotary vacuum pump has become larger than the stored container vacuum degree of the vacuum container by comparing the stored container vacuum-degree data with the pump vacuum-degree data about the vacuum degree in the vicinity of the oil-rotary vacuum pump measured by the vacuometer after the vacuum degree in the vicinity of the oil-rotary vacuum pump is obtained. an oil-rotary vacuum pump connected to the vacuum container and adapted to evacuate the vacuum container; a pair of on-off valves (121, 122) provided in series between the vacuum container and the oil-rotary vacuum pump; a vacuometer positioned between the pair of on-off valves (121, 122) and adapted to measure a vacuum degree; and a controller that controls the pair of on-off valves (121, 122) to be opened or closed based on the vacuum degree measured by the vacuometer characterized in that the controller is configured to control a vacuum-exhaust operation so that: a first on-off valve provided adjacent to the vacuum container, when the oil-rotary vacuum pump is driven, is opened for a predetermined time so as to store container vacuum-degree data about a vacuum degree of the vacuum container measured by the vacuometer; the first on-off valve is closed, and a second on-off valve provided adjacent to the oil-rotary vacuum pump is subsequently opened so as to obtain pump vacuum-degree data about a vacuum degree in the vicinity of the oil-rotary vacuum pump measured by the vacuometer; and the pair of on-off valves (121, 122) are opened when the controller recognizes that the vacuum degree in the vicinity of the oil-rotary vacuum pump has become larger than the stored container vacuum degree of the vacuum container by comparing the stored container vacuum-degree data with the pump vacuum-degree data about the vacuum degree in the vicinity of the oil-rotary vacuum pump measured by the vacuometer after the vacuum degree in the vicinity of the oil-rotary vacuum pump is obtained. a first on-off valve provided adjacent to the vacuum container, when the oil-rotary vacuum pump is driven, is opened for a predetermined time so as to store container vacuum-degree data about a vacuum degree of the vacuum container measured by the vacuometer; the first on-off valve is closed, and a second on-off valve provided adjacent to the oil-rotary vacuum pump is subsequently opened so as to obtain pump vacuum-degree data about a vacuum degree in the vicinity of the oil-rotary vacuum pump measured by the vacuometer; and the pair of on-off valves (121, 122) are opened when the controller recognizes that the vacuum degree in the vicinity of the oil-rotary vacuum pump has become larger than the stored container vacuum degree of the vacuum container by comparing the stored container vacuum-degree data with the pump vacuum-degree data about the vacuum degree in the vicinity of the oil-rotary vacuum pump measured by the vacuometer after the vacuum degree in the vicinity of the oil-rotary vacuum pump is obtained.