The time-resolved synchrotron X-ray microbeam diffraction experiment has been carried out to reveal the local layer response to the electric field in the antiferroelectric liquid crystal. The X-ray microbeam of a few mum spatial resolution was obtained with Kirkpatrick-Baez optics. The time-resolved small angle diffraction experiment was performed with a time resolution ranging from 10 mus to a few ms. The reversible local layer change between the horizontal chevron and the quasi-bookshelf structure was confirmed by the triangular wave form. The transient layer response for the step form electric field was observed. The layer response closely related with an electric field induced antiferroelectric to ferroelectric phase transition. (C) 2001 Elsevier Science B.V. All rights reserved.