The purpose of the present invention is to provide a stereoscopic endoscope optical system having high resolving power although being compact, and an endoscope provided therewith. This stereoscopic endoscope optical system is provided with a first optical system and a second optical system, wherein each of the optical systems comprises an objective optical system, a relay optical system, and an image formation optical system, the image formation optical system comprises a first lens group, a first optical path change element, and a second optical path change element, the objective optical system and the relay optical system are disposed in a first optical path, a second optical path is formed between the first optical path change element and the second optical path change element, a third optical path is formed between the second optical path change element and a final image, the first optical path change element has a first reflection surface disposed in the first optical path, and a second reflection surface disposed in the second optical path, the second optical path change element has a third reflection surface disposed in the second optical path, and a fourth reflection surface disposed in the third optical path, and the following conditional expressions (1), (2) are satisfied.(1): D1<；D2(2): D3<；D2L'objectif de la présente invention est de fournir un système optique d'endoscope stéréoscopique ayant une puissance de résolution élevée tout en étant compact, et un endoscope équipé de celui-ci. Ce système optique d'endoscope stéréoscopique est pourvu d'un premier système optique et d'un second système optique, chacun des systèmes optiques comprenant un système optique d'objectif, un système optique de relais, et un système optique de formation d'image, le système optique de formation d'image comprenant un premier groupe de lentilles, un premier élément de changement de trajet optique et un second élément de changement de trajet optique, le système optique
