N1 Cause, Reason, and Basis

~のをいいことに: meaning, usage and examples

~のをいいことに means: taking advantage of the fact that...

Updated 9 November 2026 · By the My Senpai team · Spotted a mistake? Tell us

Examples

1. 親おやがいないのをいいことに、夜遅よるおそくまでゲームをしていた。

   Taking advantage of the fact that his parents weren't home, he played games until late at night.

2. 先生せんせいが見みていないのをいいことに、テストでカンニングした。

   He cheated on the test, taking advantage of the fact that the teacher wasn't looking.

3. 上司じょうしが出張しゅっちょう中ちゅうなのをいいことに、昼休ひるやすみを長ながめに取とる社員しゃいんがいる。

   Some employees take long lunch breaks, taking advantage of the boss being away on business.

4. 誰だれも文句もんくを言いわないのをいいことに、隣人りんじんは庭にわにゴミを置おき続つづけている。

   Taking advantage of the fact that nobody complains, the neighbor keeps leaving trash in the yard.

When to use it

Says that someone takes advantage of a situation to do something they should not. The situation is usually that nobody is watching, nobody objects, or someone is absent. Example: 先生せんせいがいないのをいいことに、生徒せいとたちは騒さわいでいる (the students are being noisy, taking advantage of the teacher being away).

Nuance

Neutral register but always critical: the speaker disapproves of the action. It is used for other people's behavior, not something the speaker is proud of. The second clause is a fact, not a request or the speaker's plan.

Compare

を利用りようして is neutral and can be positive: 休やすみを利用りようして資格しかくを取とった. のをいいことに always implies selfish or improper behavior. にかこつけて uses something as an excuse or pretext: 出張しゅっちょうにかこつけて観光かんこうする. のをいいことに exploits a situation; にかこつけて hides behind a reason.

Tip: Imagine a parent saying "they took advantage of me not being home." The tone is always disapproving.