Disclosed herein are an apparatus and method for preprocessing speech signals to perform speech recognition. The apparatus includes a voiced sound interval detection unit, a preprocessing method determination unit, and a clipping signal processing unit. The voiced sound interval detection unit detects a voiced sound interval including a voiced sound signal in a voice interval. The preprocessing method determination unit detects a clipping signal present in the voiced sound interval. The clipping signal processing unit extracts signal samples adjacent to the clipping signal, and performs interpolation on the clipping signal using the adjacent signal samples.