A piezoelectric actuator has a base, and an array of drive columns separated by grooves and each having a top surface for outputting a displacement force. Each of the drive columns is formed in a unitary body with an underlying portion of the base by a first block of a plurality of green sheets made of a piezoelectric material and stacked together. The base has additionally a second block of green sheets stacked between adjacent two of the first block at the portion of the base underlying the groove.