1. A continuous tone image estimation method of a binary image, comprising the steps of: setting a plurality of kinds of scanning aperatures and a plurality of scanning apertures to be in different positions from one another for each of said plurality of kinds in the binary image selecting only one of said scanning apertures satisfying a predetermined condition for each picture element of a continuous tone image to be estimated; and estimating said continuous tone image on the basis of the number of white or black picture elements in the selected scanning aperture.