PURPOSE: To eliminate a distortion, and to execute exactly and easily the focusing by providing the first Fresnel lens on the center part of a plastic plate, and forming the second Fresnel on the other side face of its outise periphery.

CONSTITUTION: As for a glass lens 10 providing a lens part 10a on the center part and a lens part 10b on its outside peripheral part, lens which is improved extremetly a distortion of a focal image and can match a view angle is obtained. Therefore, in order to obtain a plastic lens which has the same function as this lens 10 and is lighter than this lens, the first Fresnel lens part 12A consisting of a ring zone groove 83 is formed on the center part so as to correspond to the glass lens part 10a, and the second Fresnel lens part 12B consisting of a ring zone groove 85 is provided on the other side face 84 of its outside periphery. In this way, a distortion is eliminated, a focal position is set to one point, and the focusing can be executed exactly and easily.