The invention provides a system for achieving detection and measurement of film thickness reduction of a resist pattern with high throughput which can be applied to part of in-line process management. By taking into consideration the fact that film thickness reduction of the resist pattern leads to some surface roughness of the upper surface of the resist, a film thickness reduction index value is calculated by quantifying the degree of roughness of the part corresponding to the upper surface of the resist on an electron microscope image of the resist pattern which has been used in the conventional line width measurement. The amount of film thickness reduction of the resist pattern is estimated by applying the calculated index value to a database previously made for relating a film thickness reduction index value to an amount of film thickness reduction of the resist pattern.