A capsule-type endoscope includes a capsule, an objective optical system, an image pickup element, and at least one illumination light source having a light-emitting surface, and a transparent cover. In several embodiments of the capsule-type endoscope according to the present invention, an inner surface of the transparent cover is spherical within a field of view of the objective optical system so as to have a center of curvature, the center of curvature is offset from the optical axis of the objective optical system, and a specified condition is satisfied so as to avoid flare in the objective optical system caused when light from the one (or more) illumination light source(s) enters the entrance pupil of the objective optical system. In another embodiment, the inner surface of the transparent cover has the shape of an ellipsoid. Observation methods using the capsule-type endoscope are also disclosed.
