To provide an arrangement structure in which an electronic control device for an engine can be mounted on the engine while preventing damage caused by heat from the engine for shortening wiring even in a medium to a small sized engine.

This arrangement structure having the electronic control device 20 (ECU) for the engine mounted on an upper face of a rocker cover 13 includes a bracket 25 configuring a substrate for mounting the ECU 20, a hinge 26 that openably and closably supports the bracket 25 between a normal position in which the ECU 20 is overlapped on the upper face of the rocker cover 13 and a retreated position in which the bracket 25 is deployed to the side of the rocker cover 13 with respect to a cylinder head 12, a cooling pipe 27 for the ECU 20 arranged on the bracket 25, and a pipe (a portion thereof being configured by 30a, 30b) forming a fuel circulation passage between the cooling pipe 27 and a fuel tank 40.

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