1. An image-providing device comprising: a fish-eye image input device inputting fish-eye image; a fish-eye image storage device storing said input fish-eye image; a visual-field information input device inputting in real-time visual-field information including information on sight-line direction (theta, phi) and on field angle (gamma) in visual-field area of said fish-eye image; a drawing area calculation device for calculating in real-time, using said input visual-field information, each pixel of a drawing area in a plane which is orthogonal to said sight-line direction and has an extent determined by said field angle; and a dewarping processing device determining a pixel position in said fish-eye image which corresponds to each pixel position in said calculated drawing area to form in real-time a dewarped image from the fish-eye image with its distortion removed.