An adaptive dead-time controller is provided to improve a conversion efficiency of a power converter at a low/no load condition. The adaptive dead-time controller has a reference voltage generator, an error amplifier, a comparator, an oscillator, an adaptive dead-time generator and a flip-flop. The adaptive dead-time controller outputs a gate pulse according to an output voltage and an oscillation. When power converter is at a low/no load condition, the adaptive dead-time generator delays a rising edge of an oscillation signal by a dead-time from a rising edge of a clock signal, so the frequency of the gate pulse and the power consumption of the power converter are reduced.