An endoscope apparatus includes an objective optical system mounted at a distal end portion of an endoscope, which is inserted into a tube cavity, and configured to form an image of an object in the tube cavity, the objective optical system including a focusing lens movable in an optical axis direction, a solid-state image pickup device for color image pickup configured to pick up the image formed by the objective optical system, a color separation filter being arranged for each pixel in the solid-state image pickup device, a focus adjusting mechanism configured to move the focusing lens and automatically adjust the objective optical system to a focus position in a focused state, etc. wherein, when the objective optical system is automatically adjusted to a focus position by the focus adjusting mechanism, resolving power equal to or larger than 35 µm is obtained at a focus position where a distance between the objective optical system and the object is equal to or smaller than 15 mm and, when a range in which MTF of a spatial frequency 1/(3 × P) is equal to or higher than 10% is defined as width of depth of field, the objective optical system has width of depth of field equal to or larger than 5 mm.内視鏡装置は、管腔内に挿入される内視鏡の先端部に搭載され管腔内の被写体の像を結像する、光軸方向に移動可能な合焦用レンズを含む対物光学系と、対物光学系によって結像された像を撮像する画素毎に色分離フィルタが配されたカラー撮像用の固体撮像素子と、合焦用レンズを移動して対物光学系を自動で合焦状態の焦点位置に調節する合焦調節機構等を備え、合焦調節機構により対物光学系を自動で焦点位置に調節した場合、対物光学系の被写体との距離が15mm以下となる焦点位置において、35μm以上の解像力を有すると共に、空間周波数1/(3XP)のMTFが10%以上となる範囲を深度幅と定義した場合、対物光学系は、5mm以上の深度幅を有する。
