Abstract: A chair elevating/lowering hydraulic device includes at least a foot pump 3 which absorbs oil by an ascent of an operation lever 1, which discharges oil stored by a stepping-on of the operation lever, and which discharges stored oil by a stepping-on of the operation lever to a lowest position, a check valve 5 which is opened by the oil pressure of the oil discharged from the foot pump, which is opened when the foot pump is lowered to the lowest position, and which allows the oil from the non-return side to pass to allow it to return to an oil tank through the foot pump, an elevating/lowering cylinder 7, and an accumulator 6.

Abstract: In order to solve a problem in a conventional device in which an operation lever is stepped on by a foot to supply oil to an elevating/lowering cylinder, in that since oil supply to the elevating/lowering cylinder is stopped every time the operation lever is stepped on, a seat part stops every time oil supply to the hydraulic cylinder is stopped, and in that such a device gives the person who receives technician's work shock and an uncomfortable feeling, a chair elevating/lowering hydraulic device is composed of a foot pump 3 which absorbs oil by an ascent of an operation lever 1, which discharges oil stored by a stepping-on of the operation lever, and which discharges stored oil by a stepping-on of the operation lever to a lowest position, a check valve 5 which is opened by the oil pressure of the oil discharged from the foot pump, which is opened when the foot pump is lowered to the lowest position, and which allows the oil from the non-return side to pass to allow it to return to an oil tank through the fo