An endoscope apparatus includes a removable optical adaptor and a main body optical system. The optical adaptor includes an aperture and includes a first group optical system having a negative combined focal length as a whole and a second group optical system having a positive combined focal length as a whole in order from an object side. The main body optical system includes an imaging lens configured to form an image of a light flux on an image pickup device, the light flux being transmitted through the adaptor from the object. The first group optical system includes a lens having an Abbe number of 35 or higher, and the second group optical system includes a lens having an Abbe number of 45 or lower.
