A step prismatic retro-reflector includes a main reflective corner having a shared reflective surface of a geometric single plane, a virtual step surface coming into contact with the shared reflective surface at a right angle, and a plurality of sub reflective corners. Each reflective corner has a pair of independent reflective surfaces coming into contact with each other at a right angle, and arranged along the step surface, wherein the retro-reflector elements are arranged to be alternated such that a corner ratio (l/w) of the sub reflective corners is 1.5 or more, a corner orientation of the main reflective corner deviates at an angle of 10 degrees or more with respect to a point of tangency of an incident plane, a reflection orientation thereof deviates at an angle within 10 degrees, and the corner orientations thereof deviate in the opposite direction to each other.