The ease of assembly of a radial plunger pump is improved while preventing an external leakage of liquid. A pump housing 2 in the form of a cylinder having a closed bottom contains a pintle 4 therein, which is secured to the bottom of the pump housing 2 by a bolt 6. A rotor 8 is rotatably fitted around the pintle. The rotor is formed with a plurality of radially extending cylinder bores 8a, in each of which a plunger 10 is slidably disposed. A guide ring 16 is disposed around the rotor. A motor 20 is fastened to and secured to the opening of the pump housing, and includes a drive shaft which is connected to the rotor to drive it for rotation. By allowing parts to be assembled into the pump housing in one direction, the ease of assembly is improved while preventing a liquid leakage.