The structure of a vicinal Si(111) stepped surface is analyzed by force microscopy in air to reveal a fine structure in a step bunching area, and a monoatomic step in a terrace region. Step heights of one to three monoatomic layers were also observed on a debunched Si(111) surface. These steps have low crystallographic indices [112¯], [101¯], [01¯1], [213¯], and [ 1¯2¯3]. The force microscope images were in good agreement with scanning electron microscope and reflection electron microscope images observed in ultrahigh vacuum just after sample annealing by resistive heating.