This paper proposes a new stereophonic echo canceler which can be realized by using single adaptive filter. Since most of conversations in telecommunication are single talking, Pseudo-Stereophonic Echo Canceler (PST-EC), which is a monaural echo canceler and has only been applied to pseudo-stereophonic speech sound produced by attenuating and delaying monaural sound, is applicable to stereophonic communication. To cope with double talking, stereophonic speech sound is classified into strongly correlated component (single talking) and less correlated component (double talking). Therefore, PST-EC and echo suppressors can be applied to the former and the latter component, respectively.