PROBLEM TO BE SOLVED: To provide a pump by which pumping effect can be easily obtained by taking the other approach to the conventional ultrasonic pump, and an opposing element for the pump used for the concerned pump.SOLUTION: A pump comprises: a horn part 24 having a columnar shape whose outer surface is defined by a lower surface 24, a side surface continuing to the lower surface 24and an upper surface continuing to the side surface, and includes a penetration hole 23 having a first opening Oat the center of the lower surface 24and extending toward a second opening Oprovided on the side surface; and vibration generating means provided so as to be in contact with the upper surface and for applying to the horn part 24, mechanical vibration that propagates from the upper surface toward the lower surface 24. An opposing element 21opposing to the lower surface 24is configured such that, depending on a relative positional relationship measured radially from the center of the lower surface regarding a gap formed
