Abstract: An optical filter is provided having an optical plate which has a chamfered section formed on an outer peripheral edge section of one principle surface of the optical plate and has isotropy with respect to wet-etching. The chamfered section is of an arc shape which is cross-sectionally concave in an inward direction of the optical plate.

Abstract: An object of the invention is to provide an optical filter that prevents an optical thin film formed on an optical plate from being partially removed, and prevents micro-cracks occurring in an outer peripheral edge section of a principle surface of the optical plate, and that has a high yield rate. An optical filter is provided with an optical plate which has a chamfered section formed on an outer peripheral edge section of one principle surface of the optical plate, and has isotropy with respect to wet-etching, and the chamfered section is of an arc shape which is cross-sectionally concave in an inward direction of the optical plate, and is formed by means of wet-etching. A crossing angle between the one principle surface and a concave surface where the chamfered section is formed, and a crossing angle between the concave surface and a side surface of the optical plate 3 where the chamfered section is formed, namely, crossing angles ?G and ?H are respectively 100° or greater and less than 180° .