A fuel supply system for an engine, configured to supply fuel to the engine having a plurality of cylinders, comprising: a plurality of fuel injection valves (130; 133-138) configured to inject fuel into the plurality of cylinders in a given order; a fuel distribution part having a first distribution pipe configured to distributingly supply fuel to a first fuel injection valve group comprised of some of the plurality of fuel injection valves, and a second distribution pipe configured to distributingly supply fuel to a second fuel injection valve group comprised of a remainder of the plurality of fuel injection valves, wherein the fuel injection valves (133, 135, 134) of the first fuel injection valve group and the fuel injection valves (137, 138, 136) of the second fuel injection valve group inject fuel alternately; a fuel pump part configured to discharge fuel; a first feed pipe connecting a first discharge part of the fuel pump part with the first distribution pipe; and a second feed pipe connecting a second discharge part of the fuel pump part and the second distribution pipe, wherein the first feed pipe and the second feed pipe form independent fuel feed paths from the first and second discharge parts of the fuel pump part to the first distribution pipe and the second distribution pipe, respectively, characterized in that the fuel supply system further comprises: a first pressure reducing valve configured to be opened when a pressure in the first distribution pipe exceeds a given pressure limit; a first return pipe configured to return excess fuel in the first distribution pipe when the first pressure reducing valve is opened; a second pressure reducing valve configured to be opened when a pressure in the second distribution pipe exceeds a given pressure limit; a second return pipe configured to return excess fuel in the second distribution pipe when the second pressure reducing valve is opened; and a coupling part coupled to an upstream end of the first return pipe and a downstream end of the second return pipe, and attached to the first distribution pipe. a plurality of fuel injection valves (130; 133-138) configured to inject fuel into the plurality of cylinders in a given order; a fuel distribution part having a first distribution pipe configured to distributingly supply fuel to a first fuel injection valve group comprised of some of the plurality of fuel injection valves, and a second distribution pipe configured to distributingly supply fuel to a second fuel injection valve group comprised of a remainder of the plurality of fuel injection valves, wherein the fuel injection valves (133, 135, 134) of the first fuel injection valve group and the fuel injection valves (137, 138, 136) of the second fuel injection valve group inject fuel alternately; a fuel pump part configured to discharge fuel; a first feed pipe connecting a first discharge part of the fuel pump part with the first distribution pipe; and a second feed pipe connecting a second discharge part of the fuel pump part and the second distribution pipe, wherein the first feed pipe and the second feed pipe form independent fuel feed paths from the first and second discharge parts of the fuel pump part to the first distribution pipe and the second distribution pipe, respectively, characterized in that the fuel supply system further comprises: a first pressure reducing valve configured to be opened when a pressure in the first distribution pipe exceeds a given pressure limit; a first return pipe configured to return excess fuel in the first distribution pipe when the first pressure reducing valve is opened; a second pressure reducing valve configured to be opened when a pressure in the second distribution pipe exceeds a given pressure limit; a second return pipe configured to return excess fuel in the second distribution pipe when the second pressure reducing valve is opened; and a coupling part coupled to an upstream end of the first return pipe and a downstream end of the second return pipe, and attached to the first distribution pipe. a first pressure reducing valve configured to be opened when a pressure in the first distribution pipe exceeds a given pressure limit; a first return pipe configured to return excess fuel in the first distribution pipe when the first pressure reducing valve is opened; a second pressure reducing valve configured to be opened when a pressure in the second distribution pipe exceeds a given pressure limit; a second return pipe configured to return excess fuel in the second distribution pipe when the second pressure reducing valve is opened; and a coupling part coupled to an upstream end of the first return pipe and a downstream end of the second return pipe, and attached to the first distribution pipe.