To moderate a problem of light-out and flickering caused by a driving frequency lower than a resonance frequency in a low temperature zone, and a problem of lowering in electric power efficiency caused by a too-high driving frequency in a high temperature zone, so as to allow a piezoelectric inverter for cold-cathode tube to carry out a stable operation over a wide temperature range.

A frequency control driving circuit 101 controls the driving frequencies of driving transistors Q1, Q2 to maintain a tube current flowing in a cold-cathode tube CFL to a target value. A tube current control circuit 100 including a negative characteristic thermister Rdh of a thermosensitive element is provided in a portion for imparting a voltage signal detected by tube current detecting resistance Rd to the frequency control driving circuit 101. A resistive potential dividing ratio temperature characteristic of the tube current control circuit 100 is set to increase the target value of the tube current in accompaniment to lowering of a peripheral temperature within a prescribed peripheral temperature range, and to saturate a change therein in the low temperature zone and the high temperature zone outside the prescribed peripheral temperature range.