The fundamental study of particle electrophoresis in microchannels is relevant to many applications. It has long been accepted that particles move parallel to the applied electric field in a straight uniform microchannel. This paper presents the first experimental demonstration of lateral particle migration in electrophoresis through a rectangular microchannel. This wall-induced dielectrophoresis-resembled motion is driven by the electrical force arising from the non-uniform electric field around the particle. It decays rapidly when the particle is away from the channel wall, and vanishes in the center of the channel. The observed result is a focused particle stream flowing along the channel centerline. The measured widths of the particle stream at various electric fields agree reasonably with the predictions of an approximate analytical model.