To solve a problem in a conventional suction device with a suction head exceeding several meters and a vacuum pump wherein normally much cost is required to generate a large suction head and a high vacuum since their efficiencies are very low and their devices are complicated and sophisticated.

In this suction device, an upwardly opened water storage tank 2 is connected to a closed vacuum tank 1a installed at an elevated position just above the water storage tank through a pipe and a drain control valve 6a is installed in the pipe. A pipe feeding water from the water tank to the upper part of the vacuum tank 1a by a lift pump 3 and a water feed control valve 5a are installed in the suction device. Also, a pipe for sucking the water and an automatic valve for control and a pipe for discharging air in the vacuum tank 1a and an automatic air discharge valve 7 are installed on the upper part of the vacuum tank 1a. By circulating water in vertical direction, a negative pressure due to a water level difference between the vacuum tank and the water storage tank can be generated in the vacuum tank 1a. As a result, the device equivalent to such a vacuum pump capable of easily generating a vacuum with an absolute pressure near zero or sucking at a high head can be obtained by installing the water storage tank and the vacuum tank at a level difference of approximately 10 m.