A first ignition cylinder that performs ignition first is set based on an engine stop position in automatic start. Existence/nonexistence of a misfire in the first ignition cylinder is determined based on whether a difference ΔNe between engine rotation speed at a predetermined crank angle in an interval from timing immediately before the ignition to timing immediately after the ignition of the first ignition cylinder (e.g., at TDC of first ignition cylinder) and engine rotation speed at a predetermined crank angle before ignition of a second ignition cylinder (e.g., at TDC of second ignition cylinder) is equal to or smaller than a predetermined misfire determination threshold value Nef. When misfire time number of the first ignition cylinder exceeds a predetermined value, fuel supply to the first ignition cylinder is prohibited and the automatic start is started from the second ignition cylinder.