The present invention addresses the problem of providing a variable-magnification optical system and an image pickup device provided with the variable-magnification optical system, which enable the realization of a high-resolution observation image display system that can freely change the observation visual field, while maintaining the small size of an observation optical system and without causing the operation distance of the observation optical system to change. In order to solve this problem: this variable-magnification optical system comprises a first lens group G1, which is connected to the observation optical system and is disposed closest to the observation optical system side, a final lens group (G4), which is disposed closest to the image side, and a plurality of moveable lens groups (G2, G3) which are disposed between the first lens group G1 and the final lens group and which can move in the optical axis direction and the variable-magnification optical system is configured so that the first lens group G1 and the final lens group are fixed in the optical axis direction, magnification is varied by causing the plurality of moveable lens groups to move in the optical axis direction, and focusing from the farthest-point object to the nearest-point object is carried out by causing at least one of the plurality of moveable lens groups to move in the optical axis direction.La présente invention aborde le problème consistant à fournir un système optique à grossissement variable et un dispositif de capture dimage équipé du système optique à grossissement variable, qui permettent la réalisation dun système daffichage dimage dobservation à haute résolution qui peut changer librement le champ visuel dobservation, tout en maintenant la petite taille dun système optique dobservation et sans amener la distance de fonctionnement du système optique dobservation à changer. Afin de résoudre ce problème, ce système optique à grossissement variable comprend un premier groupe
