Disclosed is an ink jet head for ejecting an ink droplet to form an image on a recording medium, including a pressure chamber to which ink is supplied, an actuator which applies a pressure on the ink filled in the pressure chamber to eject the ink droplet, a circuit applying to the actuator a drive-waveform for sequentially ejecting one or more ink droplets to form one pixel, the one ink droplet having V in volume, and a nozzle plate which has a nozzle fluidly communicating with the pressure chamber to eject ink droplet therefrom, the nozzle having a stepped inner surface shaped to include an inlet communicating with the pressure chamber and having a first sectional area in an orthogonal plane to ink-ejecting direction, and to include an outlet communicating with the inlet and having a length Ln1 in the ink-ejecting direction and a second sectional area C1 in the orthogonal plane smaller than the first sectional area, the Ln1, C1, and V being satisfied the relationship of 0.5≦Ln1/(V/C1)≦1.0. The ink jet head provides a high print quality while preventing a variation in volume of ink droplet ejected from the nozzle.