PROBLEM TO BE SOLVED: To provide an endoscope system easy to use in observation or diagnosis and also to provide a method of driving such an endoscope system.SOLUTION: An endoscope system 10 comprises: an endoscope 12 including an insertion part 12a to be inserted into an observation object, a direct-viewing observation unit 41 which has a field of view in a proximal direction of the insertion part 12a, a side-viewing observation unit 42 which has a field of view in a lateral direction of the insertion part 12a, and a second protruding portion 32 which protrudes from the insertion part 12a and forms a blind spot in the field of view of the side-viewing observation unit 42； an image acquisition unit 97 which acquires a direct-viewing observation image 111 by using the direct-viewing observation unit 41 and a side-viewing observation image 112 by using the side-viewing observation unit 42； a monitor 18 which displays the direct-viewing observation image 111 and the side-viewing observation image 112； and a display control unit 98 which masks at least a first blind spot 114 in the side-viewing observation image 112 and adjusts a relative display ratio between the direct-viewing observation image 111 and the side-viewing observation image 112 on the monitor 18.SELECTED DRAWING: Figure 6【課題】観察または診断等において使用しやすい内視鏡システム及び内視鏡システムの駆動方法を提供する。【解決手段】内視鏡システム１０は、観察対象に挿入する挿入部１２ａと、挿入部１２ａの先端方向に視野を有する直視観察部４１と、挿入部１２ａの側面方向に視野を有する側視観察部４２と、挿入部１２ａから突出し、側視観察部４２の視野に死角を形成する第２突出部３２と、を有する内視鏡１２と、直視観察部４１を用いて直視観察画像１１１を取得し、かつ、側視観察部４２を用いて側視観察画像１１２を取得する画像取得部９７と、直視観察画像１１１及び側視観察画像１１２を表示する表示部であるモニタ１８と、側視観察画像１１２のうち少なくとも第１死角部分１１４をマスクし、かつ、モニタ１８における直視観察画像１１１と側視観察画像１１２の相対的な表示割合を調節する表示制御部９８と、を備える。【選択図】図６
