1. A detecting method of detecting a specific object region located in a picture frame recorded by an image sensor, comprising steps of: sequentially creating picture frames by picking up an object sequentially; acquiring a shift amount between a present picture frame presently created among said picture frames and a previous picture frame created prior to said present picture frame among said picture frames; shifting an outline frame defined around said previous picture frame according to said shift amount on said previous picture frame, to form a normalized picture frame from an image region surrounded in said outline frame after shifting; retrieving a difference between said present picture frame and said normalized picture frame, to detect a difference region according to said difference and included in said present picture frame; detecting said specific object region in said difference region by searching said specific object region in said difference region, said searching being performed by shifting a detection region in said difference region, wherein if there is a lack of said difference region in said difference region detection for said present picture frame, said information of said specific object region obtained for said previous picture frame is used for said present picture frame; wherein an amount of shifting of a casing in which said image sensor is incorporated is measured from photographing said previous picture frame to photographing said present picture frame, and is used for said shift amount between said present picture frame and said previous picture frame; and wherein said specific object region is a human facial image region; and wherein the step of detecting said specific object region is performed on all of said sequentially created picture frames.