A retro-reflect type light pipe, an illumination device including the same, and a projection display including the illumination device are provided. The retro-reflective type light pipe includes an incident portion through which light is incident, a guide portion which guides the incident light such that the incident light propagates internally therewithin while being reflected at inner walls thereof, and which thereby mixes the incident light thus providing uniform light. A retro-reflective portion, provided at one end of the guide portion, re-reflects the incident light toward the incident portion. The illumination device includes a light source, the retro-reflective type light pipe, and an optical path-changing member provided between the light source and the retro-reflective type light pipe, which changes the direction of the light emitted from the light source such that the light from the light source propagates toward the retro-reflective type light pipe.