There is provided highly efficient discharge lamp lighting apparatus capable of reducing its cost by reducing high withstand voltage components on the secondary side of a high voltage transformer and stabilizing, its circuit operation. A discharge lamp lighting apparatus (1) comprises a high voltage transformer (2), a switching circuit (4) for driving the primary side of the high voltage transformer (2), and a triangular wave generation circuit (15) for determining the operation frequency of the switching circuit (4). The triangular wave generation circuit (15) includes a frequency switching means (25) for switching the operation frequency of the switching circuit (4) between before and after the lighting of a discharge lamp (3). At the secondary side of the high voltage transformer (2), a resonant circuit having a capacitance component consisting of only a parasitic capacitance (CCFL) is also formed. Before the lighting of the discharge lamp (3), the switching circuit (4) is operated at a frequency around the series resonance frequency of the resonant circuit on the secondary side. After the lighting of the discharge lamp (3), the switching circuit (4) is operated at a frequency around the frequency at which the phase difference between the voltage and the current on the primary side becomes minimum.