To provide a slurry pump preventing leakage of slurry by simple structure without providing a packing box.

This piston pump is provided with: a main casing 3 having a suction opening 5 and a delivery port 6 and forming a pressurizing chamber 2; a cylinder liner 4 opened to the pressurizing chamber 2; and a piston 18 slidably arranged on the cylinder liner 4 and reciprocated to thereby pressurize slurry sucked from the suction opening 5 to deliver it from the delivery port 6. The piston pump includes: a pair of piston seals 20, 20 arranged on the periphery of the piston 18 at intervals in the axial direction of the piston and forming a sealed annular clearance 21 between the periphery of the piston and the inner periphery of the cylinder liner; a lubricator 22 having two first and second chambers partitioned by a partitioning wall and transmitting slurry pressure in the pressurizing chamber to the first chamber through the partitioning wall by communication of the second chamber with the pressurizing chamber 2 with lubricating liquid stored in the first chamber; and pipe line 35 communicating the first chamber with the annular clearance 21.