A bit rate control method may include calculating a quality measure of a current frame and a mean of quality measures of two or more previous frames in order to calculate a deviation of the quality measure of the current frame from the mean of the quality measures of the two or more previous frames; comparing the deviation to a critical value measure; and controlling a quantization parameter in response to a result of the comparison. A bit rate control apparatus may include a quality measure calculator that calculates the quality measure of the current frame and the mean of the quality measures of the two or more previous frames in order to calculate the deviation; a comparator that compares the deviation to the critical value measure; and a quantization parameter setting unit that controls the quantization parameter in response to the result of the comparison.