Fuel supply pump which is lubricated by the fuel

A fuel supply pump (1) comprises a low-pressure supply pump (15) for pumping up a low-pressure fuel, and a pump element (2) having a plunger (21) for increasing the pressure of the low-pressure fuel supplied into a pressure chamber (26) by the low-pressure supply pump. Part of the low-pressure fuel discharged from the low-pressure supply pump is supplied to a pump cam chamber (37) as a lubrication fuel for sliding portions in the pump cam chamber. Part of the lubrication fuel in the pump cam chamber is sucked in by the low-pressure supply pump from a fuel film portion (38). Therefore, the lubrication fuel can be forcibly supplied to the bearing portions using the low-pressure supply pump, and thus can be supplied in a uniform flow rate to the bearing portions, thereby stabilizing the lubricating conditions of the bearing portions.