A high-pressure fuel supply pump which has no probability of discontinuity of a thin film of fuel at a sliding portion even when the fuel is not needed to be compressed to a high pressure is obtained. Two low-pressure fuel ports are provided on the high-pressure fuel supply pump in addition to a high-pressure discharge port to a high-pressure fuel capacity chamber. One of the two low-pressure fuel ports is connected to a low-pressure fuel capacity chamber and remaining one is connected to a low-pressure fuel supply pump. Accordingly, the interior of the high-pressure fuel supply pump is always filled with fresh fuel even in a mode in which a high-pressure fuel injecting valve does not inject fuel and only a low-pressure fuel injection valve injects fuel, so that a temperature rise of a plunger and a cylinder is prevented and locking of the plunger and the cylinder can be prevented.
