1. An image processing device that performs blur correction on an input picture captured through a follow shot of a subject, said image processing device comprising: a blur estimation unit configured to estimate a direction and size of a blur in each of a plurality of regions in the input picture; a clustering unit configured to perform clustering of the regions based on a similarity of the regions in at least one of the estimated direction and size of the blur; a subject region identification unit configured to identify at least one cluster corresponding to the subject, from among a plurality of clusters obtained through the clustering; and a blur correction unit configured to perform blur correction on a region belonging to the identified cluster, based on the estimated direction and size of the blur, wherein said blur estimation unit includes: a PSF size determination unit configured to determine a size of a Point Spread Function (PSF) so as to adaptively change the size of the PSF according a shape of the subject in the input picture; and a PSF estimation unit configured to estimate the direction and the size of the blur by estimating a PSF of the determined size in each of the regions in the input picture.