An optical-type rotational body position detection apparatus includes a body being rotational in a predetermined angle at each predetermined time interval to cross an optical axis between fixed light emitting and detecting units, including a standard position hole on a rotational locus crossing the axis, and configured such that after rotating the body at one interval from a standard position at which the hole coincides with the axis, a periphery of the hole is positioned outside the periphery at the standard position. The apparatus further includes a restriction unit on a support to cross the axis and to permit light passing and to restrict a diameter of the passing light. The restriction unit restricts the diameter of the passing light to be smaller than a minimum distance within a positional displacement tolerable error range of the hole after the predetermined angled rotation of the body.