A lamp driving structure for backlight module includes a backlight module implemented for disposing a first circuit board and a second circuit board thereon, the first circuit board couples with the second circuit board through a transmission line; the structure further includes at least a square wave controller, two square wave switches, a mutually coupled transformer, a plurality of driving transformers and a plurality of connectors disposed selectively on the first circuit board and the second circuit board, thereby reducing the number of driving transformers and connectors and the area of circuit boards to further reduce the manufacturing cost of the lamp driving device.