A waterproof ventilator includes: an outer hollow body including: an internal space; a side with an outer opening adopted not to be covered with a water film at a lower portion thereof; and a bottom; and an inner hollow body including an internal space, at least a part of which is housed in the outer hollow body, and including: an outer surface disposed so as not to cause a water film to stay in a gap with an inner surface of the outer hollow body; an inner opening provided at a position not to be hit directly with water entering into the internal space of the outer hollow body through the outer opening and adopted not to be covered with a water film; an upper opening provided at an upper side than the inner opening and communicating with an exterior of the outer hollow body; and a bottom.