Provided is an apparatus for detecting a speech/non-speech section. The apparatus includes an acquisition unit which obtains inter-channel relation information of a stereo audio signal, a separation unit which separates each element of the stereo audio signal into a center channel element and a surround element on the basis of the inter-channel relation information, a calculation unit which calculates an energy ratio value between a center channel signal composed of center channel elements and a surround channel signal composed of surround elements, for each frame, and an energy ratio value between the stereo audio signal and a mono signal generated on the basis of the stereo audio signal, and a judgment unit which determines a speech section and a non-speech section from the stereo audio signal by comparing the energy ratio values.