1. A target recognizing device comprising: a template storing device which stores a template for recognizing a target; an image acquiring device which acquires continuous images including said target; a recognition processing device which detects an optical flow between at least two images of said continuous images, to obtain an evaluation function value based on said optical flow; and an update device which updates said template stored in said template storing device, based on the image including said target acquired by said image acquiring device, until said evaluation function value exceeds a predetermined value.