An aspherical lens by which residual aberration in all of third eye-positions is corrected and which the center or edge thickness can be reduced. Thus, this aspherical lens employs a first or second curved surface represented by the following equation: where (x, y, z) represents the coordinates of a point on an aspherical surface and satisfies (y epsilon [a, b]) &andg& (z epsilon [c. d]); my is an order of a spline function in the direction of the y-axis (in this case, an integer which is not less than 4); mz is an order of the spline function in the direction of the z-axis (in this case, an integer which is not less than 4); ny is the number of inner knots in [a, b] in the direction of the y-axis (in this case, an integer which is not less than 4); nz is the number of inner knots in [c, d] in the direction of the z-axis (in this case, an integer which is not less than 4); Nmy,i (y) represents an ith my-th-order normalized B-spline function in the case that knots in the direction of the y-axis are xi 0, xi 1, xi 2, . . . , xi ny+2my-1 (incidentally, "i" is an integer within [o, nm+my-1] and the position of each knot meets the following condition: xi 0</= xi 1</=. . . </= xi my-1</=a< xi my</=. . . </= xi ny+my-1<b</= xi ny+my</=. . . </= xi ny+my+1; Nmz,i (z) represents an jth mz-th-order normalized B-spline function in the case that knots in the direction of the z-axis are xi 0, xi 1, xi 2, . . . , xi nz+2mz-1 (incidentally, "j" is an integer within [0, nz+mz-1] and the position of each knot meets the following condition: xi 0</= xi 1</=. . . </= xi mz-1</=c< xi mz</=. . . </= xi nz+mz-1<d</= xi nz+mz</=. . . </= xi nz+2mx-1; and ci,j is a coefficient.