A second lens frame has a shape including: a contact portion having a cylindrical shape with a diameter smaller than an inner diameter of a space portion of a first lens frame, a distal end portion thereof being brought into contact with an end face of the first lens frame; and a fitting portion having a diameter larger than that of the contact portion in a cylindrical shape fitting on an inner wall surface of the first lens frame, and when the second lens frame is inserted into the space portion of the first lens frame, a gap is formed therebetween. Accordingly, a distal end portion of the second lens frame is reliably brought into contact with an end face of a flange portion of the first lens frame, whereby variations in position in an optical axis direction are eliminated, enabling provision of a stable optical precision.