The present invention proposes a fuel pressure control apparatus for a high-pressure fuel injection system which sufficiently reduces a fuel pressure in an accumulator line (20) while preventing the high-pressure fuel injection system from being adversely affected. The fuel pressure control apparatus for the high-pressure fuel injection system is equipped with an accumulator line (20) for accumulating fuel supplied from a fuel pump (30) at a high pressure and supplying the fuel to fuel injection valves (12), and with a relief valve (22) for discharging fuel in the accumulator line (20). Furthermore, the apparatus is equipped with fuel pressure control means (68) for detecting a fuel pressure in the accumulator line (20) and driving the relief valve (22) so as to reduce the fuel pressure in accordance with a pressure reduction requirement based on a comparison between the detected fuel pressure and a target pressure. An electronic control unit (60) determines a detection timing of the fuel pressure in such a manner as to prevent a period during which the fuel pump (30) force-feeds fuel from overlapping with the detection timing of the fuel pressure by detection means (68).