The invention relates to a stereo imager that is reduced in the number of members, favorable in view of cost and less susceptible to variations from optical system to optical system. The stereo imager comprises a single image pickup device 4 and a stereo imaging optical system including bending member 21L, 21R, 22L and 22R for bending parallactic light beams from a subject and adapted to form on the single image pickup device 4 at least two parallactic images having mutual parallaxes. The stereo imaging optical system comprises at least one optical member 3 located in front of the single image pickup device 4 and adapted to receive light beams forming at least two parallactic images and have the same optical action or function with respect to each light beam.