To attain self-lubrication around a gear shaft part using an existing gear pump.

An oil suction port 31a, an oil delivery port 31b and a pair of bearing holes 26 are opened in a back face cover 23c of a pump casing 23 shown in Figure 4, and gear shafts 24a, 25a projected from a pair of gears meshed with each other are supported in the bearing holes 26. A control valve unit 21 is formed with a pump mating face 21a mounted with a back face cover 23c, and an oil collecting groove 33a is formed around an oil inflow port 32b opened to the pump mating face 21a and communicating with the oil delivery port 31b. Oil reservoir parts 21b, 21c are formed in positions opposed to the bearing holes 26, and the oil reservoir parts 21b, 21c and the oil collecting groove 33a are communicated through a leak groove 34. Oil leaking from the oil inflow port 32b is collected into the oil collecting groove 33a and led to the oil reservoir parts 21b, 21c via the leak groove 34. The peripheries of the gear shaft parts 24a, 25 are self-lubricated with the oil retained in the oil reservoir parts 21b, 21c.