In a piezoelectric transformer for a fluorescent lamp, the size of an electrode at a central region of each side on a first face is smaller than that of electrodes at the corner region thereof. As a result, the stress generated in the piezoelectric block is minimized and the heat caused by stress is prevented, so that the damage of the piezoelectric block and the deterioration of the efficiency may be prevented. The input electrode can be formed in various shapes such as diamond, cross, and rhombic shapes.