PURPOSE: To remarkably alleviate the load of a collecting operator and to lower the cost of water-collection for sampling, by automatically collecting purified water in an industrial place into a water-collecting tank at the desired time of a predetermined date, and keeping the water-collecting tank cool until its recovery for reuse.

CONSTITUTION: When a 24hr timer 4 preset by turning ON a weekly timer 8 is driven, a 60sec timer 5 attached to the timer 4 is operated for one minute to open a solenoid water-supply valve 6 for one minute. Consequently, purified waste water W which has been pumped up by a water in-take pump 14 and let flow through a water in-take pipe 12 and a water supply pipe 9 is collected by about 1l in a water-collecting tank 7. The water-supply valve 6 is then turned OFF, and the collectionand discharge of the purified water W are repeated again, so that the purified water is collected in the water-collecting tanks 7a, 7b. When each of the water-collecting tanks 7, 7a, 7b is recovered on the same day, a gate of a lower chamber 2c is opened, the tanks 7, 7a, 7b are taken out and accommodated in a vessel such as a cooler, and new water-collecting tanks are set again.