Contact between a specimen and an indenter in the nanoindentation hardness test is analyzed by using the Greenwood-Williamson model. The specimen and indenter are approximated by an elastic rough surface and a rigid smooth surface, respectively, and roughness parameters of topographical data obtained from real hardness indentations are used. Variation of Ar/An, the ratio of real contact area to nominal contact area, with the indentation load and surface roughness of the specimen is investigated. The results show that Ar/An tends to increase as the load decreases while the roughness has no significant effect on Ar/An.