A lens design method comprising: calculating a curve value of a distance vision part and a curve value of a near vision part of a progressive power lens on an object side and a curve value of a distance vision part and a curve value of a near vision part of the progressive power lens on an eyeball side by using, respectively, a radius of curvature of the distance vision part and a radius of curvature of the near vision part of the progressive power lens on the object side and a radius of curvature of the distance vision part and a radius of curvature of the near vision part of the progressive power lens on the eyeball side, changing curve data including the curve value of the distance vision part and the curve value of the near vision part on the object side and the curve value of the distance vision part and the curve value of the near vision part on the eyeball side between an upper limit value and a lower limit value that are determined by prescription values of a spherical power, an addition, an astigmatism axis, and an astigmatic power to calculate a plurality of sets of the curve data; calculating, for each of the calculated sets of the curve data, a thickness at a second position on the progressive power lens that satisfies thickness conditions for a first position on the progressive power lens, and extracting, from the plurality of sets of the curve data, the curve data in which the thickness at the second position satisfies a predetermined condition, wherein each of the curve values Ci is represented by the following expression: Ci = I − 1.0 × 1000 / R where I is the refractive index of a lens base with respect to the e-line, and R is the radius of curvature in millimeter. calculating a curve value of a distance vision part and a curve value of a near vision part of a progressive power lens on an object side and a curve value of a distance vision part and a curve value of a near vision part of the progressive power lens on an eyeball side by using, respectively, a radius of curvature of the distance vision part and a radius of curvature of the near vision part of the progressive power lens on the object side and a radius of curvature of the distance vision part and a radius of curvature of the near vision part of the progressive power lens on the eyeball side, changing curve data including the curve value of the distance vision part and the curve value of the near vision part on the object side and the curve value of the distance vision part and the curve value of the near vision part on the eyeball side between an upper limit value and a lower limit value that are determined by prescription values of a spherical power, an addition, an astigmatism axis, and an astigmatic power to calculate a plurality of sets of the curve data; calculating, for each of the calculated sets of the curve data, a thickness at a second position on the progressive power lens that satisfies thickness conditions for a first position on the progressive power lens, and extracting, from the plurality of sets of the curve data, the curve data in which the thickness at the second position satisfies a predetermined condition, wherein each of the curve values Ci is represented by the following expression: Ci = I − 1.0 × 1000 / R where I is the refractive index of a lens base with respect to the e-line, and R is the radius of curvature in millimeter. <EOS>