There is provided a discharge clamp lighting apparatus including: a transformer, a transformer driving circuit, a control circuit, in which a primary side of the transformer is driven by the transformer driving circuit lighting a discharge lamp connected at a secondary side of the transformer, a discharge sensing circuit, a signal detecting circuit detecting a voltage signal induced in the discharge sensing circuit, and a protection means stopping supply of electric power to the secondary side of the transformer according to the voltage signal detected at the signal detecting circuit, wherein the signal detecting circuit includes a signal discriminating circuit attenuating a component of a voltage signal inputted from the discharge sensing circuit, the component having a frequency equal to or lower than a predetermined value, to be equal to or greater than a secondary high-frequency pass filter, passing only a high-frequency signal caused by an abnormal discharge.