Pressure reduction device, distillation device and power generation device

A distillation device is provided with a pressure reduction container (20), a hot water supply tank (12), a hot water supply pipe (16), a hot water drain pipe (18), a hot water drain tank (14), a cold water supply tank (13), a cold water supply pipe (17), a cold water drain pipe (19), a cold water drain tank (15), and flow restrictors (21, 22, 23).  On the basis of the principle of a siphon, hot water flows from the hot water supply tank (12) to the hot water supply pipe (16), the pressure reduction container (20), the hot water drain pipe (18), and the hot water drain tank (14), and cold water flows from the cold water supply tank (13) to the cold water supply pipe (17), the pressure reduction container (20), the cold water drain pipe (19), and the cold water drain tank (15) to thereby reduce the pressure in the pressure reduction container (20).  Water vapor produced by an evaporation section (20a) is condensed by a condensation section (20b) and turns into fresh water.  The cold water drain pipe (19) also discharges gas in the pressure reduction container (20).  The pressure in the pressure reduction container (20) is reduced by using the self-weights of the hot water and the cold water by the hot water drain pipe (18) and the cold water drain pipe (19), whereby the low running cost and simply structured distillation device can be provided.