To provide a small fuel injection device for an engine for a small planing boat having good durability and maintainability.

In a fuel injection device for an engine 3 for a small planing boat for injecting fuel supplied from a fuel pump 30 by an injector 22, a fly wheel magneto 28 and a fuel pump driving pulley 29 are arranged independently from each other in the fore-and art direction of a crank shaft 11 whose front and rear end parts are rotatably supported by bearings 24, 25, and the fuel pump is driven by the fuel pump driving pulley 29. Since the fuel pump driving pulley 29 for driving the fuel pump 30 is installed on a part (namely, a part where the crank shaft 11 is vibrated slightly) near a bearing 25 of an end part of the crank shaft 11, respective vibrations of the fuel pump 30 driven by a rotary power transmitted from the crank shaft 11 through the fuel pump driving pulley 29 and fuel piping are suppressed in a small level so as to improve durability.