To provide a fuel injection device with a needle valve to be opened/closed depending on a difference between valve closing force tending from the upper face side to the seat portion side of the needle valve and valve opening force tending from the seat portion side to the upper face side, reducing the exhaust amount of hydrocarbon and black smoke by reducing the pressure loss of fuel while increasing the valve closing speed during closing the needle valve to produce higher quality injection at finishing fuel injection and improve combustion for higher heat efficiency and less fuel consumption.

The fuel injection device for an internal combustion engine uses a needle valve opening/closing means for opening/closing the needle valve of a fuel injection valve depending on a difference between valve closing force tending from the upper face side of the needle valve to the seat portion side of the needle valve and a nozzle body and valve opening force tending from the seat portion side to the upper face side. The fuel injection valve has a dynamic pressure generation part formed on a seat portion, where a flow path has an area smaller than an upper passage formed on the upstream side of the seat portion to increase the flow rate of fuel.