In the present invention, the viewing area is sufficiently enlarged, and an adequate level of illumination light is distributed in the enlarged viewing area. Provided is a capsule endoscope in which an objective lens unit (11) includes, at the extreme object side, a lens which is a meniscus lens having negative power and disposed with the convex surface thereof towards the object side, so that the convex surface thereof faces the exterior. An illumination unit (13) includes a light source and an illumination window member (19). The light source is disposed so as to surround the circumference of the lens. The illumination window member is formed in an approximately circular ring shape that surrounds the circumference of the lens and is positioned closer to the image side than an outermost diameter section in the convex surface of the first lens, through which a light flux passes. A light-blocking member that blocks the entry of illumination light into the objective lens unit is disposed between the illumination window member and the lens. Conditional expressions (1) and (2) below are satisfied: −10<；f1/f<；−40.7<；d1/f<；2 where f1 is the focal length of the lens, f is the focal length of the objective lens unit, and d1 is the distance between the lens and another lens disposed adjacent to the image side of the lens.
