PROBLEM TO BE SOLVED: To provide a photography auxiliary device and an image generation system capable of reliably detecting, from an image photographed for stereoscopic image generation, a mark indicating that the image is used for stereoscopic image generation.SOLUTION: A first planar mirror of the photography auxiliary device is provided inside a housing and on the right side of a light emission part of the housing at photographing time, and reflects light incident from a first light incident part of the housing. A third planar mirror reflects light from the first planar mirror to the light emission part side. A second planar mirror is provided inside the housing and on the left side of the light emission part, and reflects light incident from a second light incident part of the housing. A fourth planar mirror reflects light from the second planar mirror to the light emission part side. A mark is disposed in a region, on the reverse side of the housing, between the light emission part and the first planar
