round-trip 
往復旅行の
A type of ticket for travel to a destination and back to the original point of departure (ant.: one-way)
例文
These days one-way tickets are almost as expensive as discount round-trip tickets.
＜ゴガクル＞より引用の例文
Should I buy a one-way ticket or a round-trip ticket?
片道切符を買ったほうがいいですか、それとも往復切符を買ったほうがいいですか？
How much is a return ticket to...uh...see the windmills?
往復切符はいくら？ ええと…風車を見に行くには？