An imaging device includes a radially-retracting device for moving a radially-retractable optical element, serving as part of a photographing optical system, between a photographing position on a common optical axis and a radially-retracted position; a biasing device for biasing the radially-retractable optical element toward the photographing position; a positioning device which determines a movement limit of the radially-retractable optical element in the biasing direction of the biasing device; and a sub-positioning device for positioning the radially-retractable optical element at the photographing position in a direction intersecting the driving direction of the radially-retracting device in a plane orthogonal to the common optical axis when the radially-retractable optical element is held at the photographing position by the positioning device, and for releasing the positioning of the radially-retractable optical element at the photographing position in the intersecting direction when the radially-retractable optical element is positioned at the radially-retracted position.