To perform gray scale printing in low cost by a simple structure in a printing head for a bubble jet printer injecting ink by air bubbles.

A printing head has a structure equipped with a nozzle plate 30 having nozzle orifices 110 having a predetermined shape formed thereto, a substrate 40 forming the chamber 50 connected to the nozzle plate 30 to receive the supply of ink, a plurality of the electrodes 70 attached to the substrate and the heating unit connected to a plurality of the electrodes 70 and having a plurality of heating elements different in size laminated and arranged thereto. By selectively applying voltage across a plurality of the electrodes 70, the heat generating surfaces of the heating elements are changed to control the size of the air bubble in ink.