Conditions for applicability of mean field theory to the thermodynamics of the ⁴He crystal surface are determined. Although the faceting transition itself is of Berezinsky—Kosterlitz—Thouless type, the thermodynamic potential outside a narrow neighborhood of the transition temperature can be expanded in the spirit of the Landau theory of second-order phase transitions. The Ginzburg—Levanyuk parameter is estimated. The singular behavior of the surface stiffness near critical directions observed for essentially non-critical temperatures is explained.