To provide a device for mixing powder and liquid by which powder and liquid can be sufficiently mixed without causing trouble of clogging near a feeding port of powder such as powdery active carbon.

A device 10 for mixing powder and liquid is provided with: a guide member 11 whose horizontal section is contracted from a powder receiving port 12 in the upper part to a powder discharging port 13 in the lower part thereof, an ejector 15 whose suction part 15a is connected to the powder discharging port 13; first liquid feeding means 16, 17, 18 for feeding liquid to the ejector 15; and second liquid feeding means 22, 27, 28, 18 for feeding liquid to the guide member 11 so as to cause the liquid to flow down along the inner wall surface of the guide member 11. In this way, powdery active carbon can be stably and surely led into the ejector 15 to stably and surely mix the powdery active carbon and water.