1. A method for estimating a cross-sectional shape of a pattern, the method comprising: a learning process step of acquiring learning data which includes SEM images of patterns having various cross-sectional shapes, and selecting an estimation engine adapted to estimate the cross-sectional shape of the pattern; and a performance process step of processing a SEM image obtained by imaging the pattern formed on a sample by use of a SEM, calculating a characteristic quantity of the SEM image, processing the calculated characteristic quantity using the selected estimation engine, and estimating the cross-sectional shape of the pattern formed on the sample; wherein, in the performance process step, information on the estimated cross-sectional shape of the pattern on the sample is output with information on reliability of estimation results.