An image pickup optical system 6 for an endoscope is provided with: a first optical member group 10 including an objective optical member disposed on the side closest to the subject a first lens barrel 11 that holds the first optical member group 10 a second optical member group 12 disposed on the image side of the first optical member group 10 and a second lens barrel 13 that holds the second optical member group 12. Optical members 20 and 21 of the first optical member group 10 are in contact with each other in the optical axis direction, the first lens barrel 11 and the second lens barrel 13 are fitted in each other in the optical axis direction, and when the first lens barrel 11 and the second lens barrel 13 are fitted in each other, the optical member 21 of the first optical member group 10 comes into contact with the second lens barrel 13, said optical member being disposed on the side closest to an image. In a state wherein the optical member 21 is in contact with the second lens barrel 13, spaces are disposed in the optical axis direction on the image side of the image side end of the first lens barrel 11, and on the subject side of the subject side end of the second lens barrel 13, and the first lens barrel 11 and the second lens barrel 13 are bonded to each other such that the first lens barrel and the second lens barrel can be separated from each other.Linvention concerne un système optique de capture dimage 6 pour un endoscope qui est muni de : un premier groupe déléments optiques 10, comprenant un élément optique dobjectif placé sur le côté le plus proche du sujet une première monture dobjectif 11 qui maintient le premier groupe déléments optiques 10 un second groupe déléments optiques 12 placé sur le côté image du premier groupe déléments optiques 10 et une seconde monture dobjectif 13 qui porte le second groupe déléments optiques 12. Les éléments optiques 20 et 21 du premier groupe déléments optiques 10 sont en contact lun avec lautre dans la direc
