An oblique-viewing endoscope includes: an endoscope axis that is a longitudinal direction of an endoscope distal end portion; an optical axis of a lens, the optical axis being an observing direction, the endoscope axis and the optical axis being disposed to form a predetermined inclination angle with respect to each other; a rectangular semiconductor package including an imaging sensor configured to convert an optical image formed by the lens to an image signal, and a terminal formed on a back face of the semiconductor package; and a rigid substrate including a semiconductor package mounting area in which the semiconductor package is mounted, an electronic component mounting area in which an electronic component is mounted, and a cable mounting area in which a cable is mounted.