To provide a compact and lightweight device which can reduce the size and weight of a device as a whole and can detect a relative position between a head and a hand of an observer in accordance with a change in a direction of an observed person or a change in an observation direction desired by an observer Providing an oral cavity observation apparatus capable of observation while maintaining an observation posture.A first housing (10) including a first mirror (11) for deflecting light from a person to be observed and a second mirror (12) for deflecting light deflected by the first mirror, a first housing And an eyepiece lens barrel (20) capable of enlarging and observing an image formed by light deflected by the second mirror. A first mirror, a second mirror, and an eyepiece barrel are arranged in order from the observed person side on the observation light path, The first mirror is configured to be rotatable with respect to the first housing about an axis passing through an intersection point P of the incident optical axis and the output optical axis or in the vicinity of the intersection point, and the first housing, the second mirror, and the eyepiece tube The observer can observe the observed image from the same direction of the observed person by rotating the first mirror in accordance with the variation of the direction of the observed person.BACKGROUND OF THE INVENTION【課題】装置全体を小型・軽量化でき、且つ、被観察者の向きの変動又は観察者が所望する観察方向の変動に追従して、観察者の頭と手との相対的な位置が真っ直ぐな観察姿勢を保持した状態で観察可能な口腔観察装置の提供。【解決手段】被観察者からの光を偏向する第1ミラー11と第1ミラーで偏向された光を偏向する第2ミラー12を備えた第1筐体10と、第1筐体に接続され第2ミラーで偏向された光による像を拡大観察可能な接眼鏡筒20とを有し、観察光路上には被観察者側から順に第1ミラーと第2ミラーと接眼鏡筒が配置され、第1ミラーが、入射光軸と出射光軸との交点P又は交点近傍を通る軸を中心として第1筐体に対して回転可能に構成され、第1筐体、第2ミラー及び接眼鏡筒を静止させた状態で、被観察者の向きの変動に応じて第1ミラーを回転させて、被観察者の同じ方向からの観察像を観察できるようにした。【選択図】図1
