Abstract: A fuel injection port 21 formed in a seat 20 is opened and closed by a movable valve 14 supported by a flat spring 16. The movable valve 14 is biased by an elastic force of a coil spring 26 in a direction that closes the fuel injection port 21. When electric power is supplied to a solenoid coil 4, the movable valve 14 is moved to a direction that opens the fuel injection port 21 as a result of an electromagnetic attraction force between a magnetic circuit M for generating an electromagnetic attraction force and the movable valve 14. Air gaps G0, G1 and G2 are formed within the fuel injection port and permeance ratios between the air gaps may be set to optimal values.