An ink jet head that prevents pressure interference between nozzles without incurring an increase in size is provided. A pressure change buffer is provided for preventing pressure interference in this ink jet head can also be easily formed with the desired characteristics. An ink reservoir 1010, orifice 1008, and ejection chambers 1006 are formed in a horizontal arrangement between the nozzle plate 1002 and cavity plate 1003 of this ink jet head 1001. Pressure change buffer 1022 for buffering pressure change in the ink reservoir 1010 is formed in a first wall 1010b, which is part of the wall determining the shape of the ink reservoir 1010. It is therefore possible to prevent pressure interference between nozzles without incurring an increase in size. In addition, the pressure change buffer 1022 can be easily formed with the desired operating characteristics.