First to fourth lenses are aligned in an optical axis direction by a lens-barrel of a camera, an O-ring is disposed between the first lens and the lens-barrel, an O-ring is disposed between the fourth lens and the lens-barrel, a space is formed between the first and second lenses, a space is formed between the second and fourth lenses, a space is formed between the third and fourth lenses, and flow of air between the spaces is precluded. The camera thus configured is free of dewing on the lens or a protective plate exposed to the exterior, even when the inside temperature is raised due to heat generation in a CCD or a mounting substrate on which the CCD is mounted.