The invention provides a flexual vibration mode piezoelectric transformer, which comprises a structure of five stacked layers, wherein the first, second, fourth and fifth layers are piezoelectric ceramic layers; the third layer is a metal layer; the directions of polarization of the first and fifth layers are same along the thickness direction, while the directions of polarization of the second and fourth layers are opposite along the thickness direction; an insulating layer is respectively arranged between the first layer and the second layer and between the fifth layer and the fourth layer; a conducting layer is respectively arranged between the second layer and the third layer and between the third layer and the fourth layer; conducting electrodes are arranged on the upper and lower surfaces of the first and fifth layers; and conducting electrodes are arranged on adjacent surfaces of the second layer and the first layer, and adjacent surfaces of the fourth layer and the fifth layer. On the basis of the working principle and performance characteristics of a vertical vibration mode piezoelectric transformer, the invention provides the flexual vibration mode piezoelectric transformer dependent on a planar electromechanical coupling factor kp; and the flexual vibration mode piezoelectric transformer can obtain low-frequency fundamental wave vibration in a small physical dimension, and installation points are accurate and firm.