A small, thin, light piezoelectric transformer capable of large-capacity output is provided at low cost. In piezoelectric transformers adjacent to each other in the row direction, a lower electrode extends in the column direction in a supporting substrate, so as to connect a plurality of piezoelectric transformers arranged in the column direction. Referring to FIGS. 2(a) and 2(b) as well, the piezoelectric substrates of the piezoelectric transformers adjacent to each other in the row direction are connected via the lower electrode or an upper electrode wire that collectively connects the piezoelectric transformers arranged in the column direction. Meanwhile, the piezoelectric substrates of the piezoelectric transformers adjacent to each other in the column direction are connected via a right electrode wire or a left electrode wire that collectively connects the piezoelectric transformers arranged in the row direction. With this structure, by applying a voltage between the cross right electrode wire or left electrode wire and the upper electrode wire or the lower electrode that crosses the wires, it becomes possible to gain access to an arbitrary set (pair) of piezoelectric transformers. Note that, upon access, four piezoelectric transformers adjacent to one another in the row and column directions are operated. While it goes without saying that more piezoelectric transformers can be operated by applying a voltage to the electrodes, operation is based on a set of four piezoelectric transformers.