A capsule endoscope includes an objective lens (1) and a transparent dome (2) that covers the object side of the objective lens (1), and the transparent dome (2) has negative refracting power. In the capsule endoscope of the present invention, the center of curvature of the object-side surface of the transparent dome (2) disagrees with the center of curvature of the objective-lens-side surface of the transparent dome (2) to satisfy the following condition: Rb < L ‰ Ra where Ra is the radius of curvature of the object-side surface of the transparent dome, Rb is the radius of curvature of the objective-lens-side surface of the transparent dome, and L is a distance from the vertex of the object-side surface of the transparent dome to the most object-side surface of the objective lens.
