PROBLEM TO BE SOLVED: To provide a user-friendly endoscope apparatus with a simple configuration that reduces positive reflection light for a subject in which positive reflection light is conspicuous, and illuminates a subject without reducing an illumination light amount for a subject in which positive reflection light is not conspicuous so that an eye-friendly image can be acquired.SOLUTION: An endoscope apparatus 1 includes: an insertion part 2 an adapter 6 that can be attached to/detached from the tip 11 of the insertion part 2 an observation window 31 provided to the adapter 6 on which reflection light from a subject is incident an illumination window 32 provided to the adapter 6 for emitting illumination light to the subject and a circular polarization part 35 provided to the adapter 6 which is a circular polarization member having a 1/4 wavelength plate 36 and a polarizing plate 37, in which when the adapter 6 is mounted on the tip 11, the 1/4 wavelength plate 36 is arranged on a subject side with respect to the polarizing plate 37, and which transmits the reflection light and the illumination light.COPYRIGHT: (C)2016,JPO&INPIT【課題】簡単な構成で、正反射光が目立つ被写体に対しては正反射光を低減し、正反射光が目立たない被写体の両方に対しては照明光量を低下させないで被写体を照明して見やすい画像を得られる、使い勝手の良い内視鏡装置を提供する。【解決手段】内視鏡装置1は、挿入部2と、挿入部2の先端部11に着脱可能なアダプタ6と、アダプタ6に設けられ、被写体からの反射光が入射する観察窓31と、アダプタ6に設けられ、被写体へ照明光を出射する照明窓32と、アダプタ6に設けられ、1/4波長板36と偏光板37を有する円偏光部材であって、アダプタ6が先端部11に装着されたときに、1/4波長板36は偏光板37に対して被写体側に配置され、反射光と照明光が透過する円偏光部35と、を有する。【選択図】図4