LENS UNIT, LENS UNIT MANUFACTURING METHOD AND IMAGING DEVICE

PROBLEM TO BE SOLVED: To provide a lens unit manufacturing method and imaging device that can attain reduction in costs as securing an optical performance.SOLUTION: A lens unit includes: a lens L3 that is provided with a flange part L3c formed in an area around an optical surface L3b; and a holding frame 54 holding a lens. The lens is shaped like a circle in which a shape of the flange part has a cut-off part L3a in a part, and n pieces of reception parts are provided in an inner periphery of the holding frame. When assembling the lens into the holding frame, at least one piece of the reception part does not abut with respect to the flange part of the lens, but a phase exists in the reception parts other than the one piece of the reception part. Assuming the flange part is a perfect circular flange part of the same diameter without the cut-off part, a point where the perfect circular flange part in a cross section of a direction orthogonal to an optical axis contacts with the reception part satisfies a following expression providing an angle at which the cut-off part extends with an optical axis of the lens as a reference is θ(°). θ