Abstract: An image is picked up by a camera comprising a fisheye lens having a relationship of h=n.multidot.f.multidot.tan(.theta./m), wherein h is the height of an image of a subject at a certain point, f is the focal distance of the fisheye lens, .theta. is a field angle, m has a value of 1.6.ltoreq.m.ltoreq.3, and n has a value of m-0.4.ltoreq.n.ltoreq.m+0.4, and the image data of which is output from the camera, is converted into a plane image by an image data processing unit, and this converted image is then output to a monitor unit. Preferably, n and m both equal 2.