Disclosed is an optical thin film deposition device that can produce an optical thin film with excellent optical properties, and a method for fabricating optical thin films at low cost and with excellent optical properties. Disclosed is an optical thin film deposition device that deposits a deposition substance onto a substrate (14) inside a vacuum chamber (10), and that is equipped with a domed substrate holding means (12) which is disposed inside the vacuum chamber (10) and holds the substrate (14), a rotation means which rotates the substrate holding means (12), a deposition means (34) which is disposed facing the substrate (14), an ion source (38) which irradiates ions toward the substrate (14), and a neutralizer (40) which irradiates electrons toward the substrate (14). The ion source (38) is disposed in a position in which the axis on which ions from the ion source (38) are irradiated is in the range not less than 8 and not greater than 40 relative to a line perpendicular to the surface of the substrate (14), and in which the ratio of the distance in the plumb direction between the center of the rotational axis of the substrate holding means and the center of the ion source (38) is in the range not less than 0.5 and not greater than 1.2.