PURPOSE: To allow an entire side face of a resin layer to arrive at an outside of an optical effective diameter without increasing an outer diameter of a base material by forming a desired resin layer in molds for an optical element when a difference δbetween an effective diameter of a surface of the layer and a diameter of a base material of the element to an unevenness Δx of a maximum diameter of the layer is large and setting a molding surface interval of a part out of an effective diameter of the molds and a molding surface of the same base material to a formula or less.

CONSTITUTION: When an interval between a base material 2 and a mold 1 is (t), the mold 1 is pressed to recess an intermediate part 3a of a resin layer 3 at the time of molding to a central axis side. When a maximum diameter of the layer 3 is Dmax, a minimum diameter is Dmin and its difference is,ΔD, at the time of 0.5t of the interval, its maximum diameter is D'max, its minimum diameter is D'min, and its difference is ΔD', ΔD=2ΔD' is satisfied. When the (t) is set to a half, ΔD/2 becomes about a half, and relationship of (t)= 32.4 + 3.76ΔD is satisfied. Accordingly, when a difference of the effective diameters is δ, an interval of out of the effective diameters may be set to (32.4 +3.76δ) or less. In fact, since unevenness of the Δx occurs in the maximum diameter of the layer, it is necessary to set the interval to (32.4+3.76 (μ-Δx)μm or less.