A fuel injection quantity control device includes: vehicle speed detection unit; gear position detection unit; engine revolution speed detection unit; accelerator opening degree detection unit; target acceleration value computation unit for finding a basic target acceleration value corresponding to the difference between the set limit vehicle speed and an actual vehicle speed and an upper limit value and lower limit value of the basic target acceleration value for each gear position in a map, limiting the basic target acceleration value with the upper limit value and lower limit value, and determining a target acceleration value; basic fuel injection quantity for vehicle speed limit computation unit for determining a basic fuel injection quantity for vehicle speed limit by feedback computation from the difference between the determined target acceleration value and the actual acceleration value; an accelerator required injection quantity computation unit for computing an accelerator required injection quantity from the engine revolution speed and accelerator opening degree; and vehicle speed limit injection quantity computation unit for selecting the smaller of the basic fuel injection quantity for vehicle speed limit and accelerator required injection quantity and setting it as a fuel injection quantity for vehicle speed limit.