Provided is a method that restores a differential quantization parameter of a current coding unit, generates a quantization parameter predictor of the current coding unit using one or two quantization parameters of a left quantization parameter, an above quantization parameter and a previous quantization parameter and generates a quantization parameter of the current coding unit using the differential quantization parameter and the quantization parameter predictor, wherein a minimum size of quantization unit is adjusted per picture. Therefore, the complexity of the encoding and decoding apparatus is reduced by adjusting the minimum size of the quantization unit. Also, coding efficiency is improved by encoding the quantization parameter using neighboring quantization parameters and by signaling the minimum size of the quantization unit per picture.