A surface effect on the behavior of solid-liquid phase transition is studied by the Landau theory. We calculate the dependence of melting temperature of a small particleon its surface curvature. We show that taking account of the effect of the curvature is essential in understanding the melting process of small particles, particularly when their radii are in the order of nm. The non-linear relationship between a melting point and a reciprocal radius is derived from a difference between the radius-dependence of the “surface-induced melting temperature (Tst)” and that of the “particle melting temperature (Tend).” The calculated results agree satisfactorily with the recent experimental data. We also show that a surface melting state becomes difficult to observe as the particle radius decreases down to a critical value. This is in contrast to the common belief that surface-induced melting becomes more dominant for smaller particles.