A fuel injection device has a two-way control valve driven by a two-position actuator. The control valve directly controls oil pressure in a back pressure chamber to control an injection operation of an injection nozzle. A two-position three-way flow passage switching valve operated by control pressure of the control valve selectively connects a control chamber of a pressure intensifier with a fuel supply passage leading to a pressure accumulator or a pressure release passage leading to a low-pressure system to indirectly control oil pressure in the control chamber. The flow passage switching valve starts a pressure intensifying operation in retard of the injection operation. When pressure is supplied to the control chamber, stoppage of the pressure intensification operation and returning operation of the pressure intensifier do not lag behind the injection operation.