PURPOSE: To provide a radial piston pump capable of increasing self-priming capability, and delivering two independent types of fluid with a short radial length.

CONSTITUTION: Two types of cylinder chambers 15a and 15b having different depth are alternately and radially arranged in a cylinder block 6, and passages 17a and 17b continuous from each of the chambers 15a and 16b to a valve plate 10 are provided. In addition, inlet ports 21a and 21b and outlet ports 22a and 22b are so formed through the valve plate 10 as to be continuous to outlet passages 19a and 19b. Also, each of the cylinder chambers 15a and 15b is fitted with a balance piston 11. As a result the axial direction length can be made smaller than the case of a radial piston pump having two rows of a cylinder group in an axial direction. Furthermore, a pressure balance in an axial direction can be maintained with the balance piston 11, and the ports of the valve plate 10 can be made larger, thereby improving self-priming capability.