An audio playback device having a function for adjusting a playback speed, and a method thereof includes, in the audio playback device, stored audio data is decoded and converted into an audio stream in a PCM format, and the audio stream is divided into a high frequency band and a low frequency band at cut-off frequency. The audio stream of the high frequency band is signal-processed using an overlap add (OLA) algorithm, and the audio stream of the low frequency band is down-sampled and signal-processed using a synchronized overlap and add (SOLA) algorithm. Accordingly, calculation time of the stream processor 130 is minimized so that a TSM function is efficiently implemented.