To improve durability by simplifying a structure of a bearing through a process of preventing the bearing from being brought in direct-contact with slurry having high pressure and high condensation.

In an oscillating pipe-type piston pump provided with a hopper 1 on which a pair of suction and discharge ports are provided, a pair of pump cylinders 4 whose one side ends are opened to the suction and delivery ports, and an oscillating pipe 2 provided in the hopper so as to be oscillated, and whose rear end is gradually moved to the position facing a pair of suction and discharge ports, and for switching suction and discharge of a piston pump, an oscillating pipe shaft 10 for oscillating the oscillating pipe 2 is so provided as to perforate through the back wall 1b of the hopper 1 and so as to extend rearward. The oscillating pipe shaft 10 is turnably supported by an oscillating pipe shaft bearing 15 provided on the back wall 1B and an oscillating shaft rear bearing 18 provided in the rear of the back wall 1B through a shaft housing 17, and the front end of the oscillating pipe 2 is connected to a discharge pipe 9 through a joining ring 16.