A structure for holding a decentered lens inside a lens barrel, as well as an axisymmetrical lens. The structure includes: a lens barrel with a lens receiving part projecting inwardly and radially from an inner surface thereof; a decentered lens, with a first lens surface as a reference surface a centering axis of which is made to coincide with an axis of the lens barrel, and a second lens surface, which includes an annular flat surface around the second lens surface, in which the annular flat surface forms a recessed surface relative to the second lens surface, in which the annular flat surface is perpendicular to the axis of the lens barrel, and in which the annular flat surface contacts the lens receiving part of the lens barrel; and a washer, installed on the inner surface of the lens barrel, to fixedly hold the decentered lens, relative to the lens barrel, by pinching the decentered lens between the washer and the lens receiving part of the lens barrel.