An ink jet head includes a heater board having a substrate on which a plurality of energy generating elements for generating energy utilized to discharge ink are provided, and a wall member joined to the heater board. The wall member has a plurality of flow passage walls which partially define flow passages, and the energy generated by the energy generating element acts through the flow passage so as to act on the ink to discharge the ink. The flow passages are fully defined when the heater board is joined to the wall member. A recessed portion provided in the heater board of the ink jet head is positioned between adjoining energy generating elements. The recessed portion has a bottom surface located at a position which is lower than a position for a heat acting surface of the heater board along which heat is transmitted to the ink. The flow passage walls of the wall member abut the heater board at the bottom surface. Consequently, any pressure wave generated by the energy generating element is not released to an adjacent flow passage, and crosstalk between the adjoining flow passages can be prevented. As a result, an ink jet head exhibiting excellent printing quality can be provided.