A pump includes an ink pressurizing chamber, an inlet port and an outlet port communicating with the chamber, a first valve member provided near the inlet port, a second valve member provided near the outlet port, a pressure adjustment channel communicating with the chamber, an electrode provided on a wall surface forming the channel, a driver IC which applies a voltage to the electrode, an insulating film provided on a surface of the electrode and in which when the voltage is applied to the electrode a wetting angle of ink on a surface of the insulating film is greater than that when no voltage is applied to the electrode, and a common electrode always in contact with ink in the chamber and held at a ground potential. Accordingly, a pump having a simple structure without any movable parts and with a low noise and less energy consumption can be provided.