To provide an ink jet head which can be configured with densely arranged nozzles and driven at high frequency and further, is free from mutual interference between nozzles.

This ink jet head comprises a pressure generating chamber 1 which generates pressure, a nozzle 2 which discharges ink, a reservoir 14 which reserves ink and a supply aperture 6 which communicates with the pressure generating chamber 1 and the reservoir 14. In the reservoir 14, a film wall is formed adjacent to the supply aperture 6. The relationship λ≤2w is established between the oscillating wavelength λ of the film wall induced by the pressure oscillation of an intrinsic oscillation period T to be determined by the nozzle 2 and the pressure chamber 1, and the span (w) of the film wall.