To provide an injection timing adjustment device of an electronic fuel injection device and an injection timing adjustment method in which a deviation of a timer piston position and a duty ratio at a low rotation is appropriately processed and a following delay of injection timing at the time when an engine rotation is raised from the low rotation is improved.

In the case where an engine rotation is decreased, a driving duty ratio of a timer control value is varied to the latest angle (0%) side and a timer piston position reaches to the latest angle position before the duty ration reaches to 0%, the duty ratio is fixed to a value at the time when the timer piston position reaches to the latest angle position. In the case where a revolution number of engine is rapidly increased, an actual timer piston position is immediately followed to a target timer piston position by varying it from the duty ratio fixed.