In the short letter, we explain an improved transform theory for colloidal-probe atomic force microscopy (CP-AFM). CP-AFM can measure a force curve between the colloidal probe and a wall surface in a colloidal dispersion. The transform theory can estimate the normalized number density distribution of the colloidal particles on the wall from the force curve measured by CP-AFM. The transform theory is important for study of the stratification of the colloidal particles on the wall, which is related to fundamental studies of colloidal crystal and glass.