Provided are an audio encoding method and apparatus capable of fast bit rate control. The audio encoding method includes: converting audio sampling data into frequency domain data; adjusting a scalefactor value in each predetermined frequency band based on an available bits and allowed distortion of a psychoacoustic model to allocate a number of necessary bits to the frequency domain data and quantize the frequency domain data; and generating a bit stream based on the quantized data. The quantizing of the frequency domain data includes: obtaining the available bits for the frequency domain data; obtaining the common scalefactor value satisfying that the used bits is not larger than the available bits, using a difference the available bits and the used bits to quantize the audio data; calculating quantization noise in the each predetermined quantization band; and adjusting a scalefactor value of a quantization band in which the quantization noise exceeds the allowed distortion of the psychoacoustic model to quantize the audio data.