Atomic structure of Si(1 1 3) 3×2 reconstructed surface was examined by high-resolution transmission electron microscopy (HRTEM). Cross-sectional atomic structure of the Si(1 1 3) 3×2 was observed along [ 1 ̄ 1 0] direction at specimen temperature of about 800 K inside an ultrahigh vacuum transmission electron microscope. Simulated images for some probable structure models were compared with the experimental HRTEM images. It was found that, if void area in Ranke’s model is filled by adatom so that a row of adatoms is created, the simulated HRTEM image shows good agreement with the observed one. The structure model recommended by Dabrowski et al. [Surf. Sci. 331–333 (1995) 1022; Phys. Rev. Lett. 73 (1994) 1660] was not able to explain the HRTEM images obtained in the present work.