It is usually said that する時 refers to the time before the action begins, while した時 refers to the time after the action is concluded. For example:

日本に着いたとき、すぐにWi-Fi使えるかな? The person is referring to the time when they have already arrived in Japan.

運転をするとき、メガネをかける。The person puts on their glasses before they start to drive.

(The example sentences are from Tofugu). This explanation also seems to agree with this distinction.

However, I found the following when listening to a podcast. The speaker (a Japanese teacher) is organizing an online event with some of his listeners. He is asking them to promise not to fight during the event:


Despite the verb form 話をする時, the speaker clearly is talking about the expected behavior during the event, not before the event begins. What do you think of this usage? Is it correct? If so, what makes it correct?

  • 1
    運転をするとき、メガネをかける means the person wears their glasses when they drive.
    – aguijonazo
    Commented Jul 4 at 1:30

1 Answer 1


~するとき is basically just "when X", and it can be used like either "before X" or "while X" depending on the context and the type of the verb. Compare:

  1. 食べるときは手を洗ってください。
    Wash your hands when you eat it.
  2. 食べるときはお箸を使ってください。
    Use chopsticks when you eat it.

While 食べるとき (= "when you eat it") is used in both cases, Sentence 1 is closer to "before eating it" and Sentence 2 is closer to "while eating it". Both in English and Japanese, you have to determine which meaning is intended based on common sense rather than grammar. For another example, いつも勉強するときに音楽を聴いています is technically ambiguous, but this normally means this person listens to music while studying, not before studying.

If the difference is important, you can always use unambiguous expressions including ~する前に ("before X") and ~している間 ("while X"), but that is not to say ~するとき should be avoided in general.

  • thank you! Your explanation is very clear. There is just one more detail I would like to address if that's ok. I interpret your example sentences to be about instructions to be followed every time something happens (1. and 2.) and habits (いつも勉強するときに音楽を聴いています). The excerpt I posted is about one-time events. For some reason, my brain thinks of this as a very different category. If what you say also applies to one-time (future) events, would it be ok for me to say something like this? 明日彼と一緒に食べるときにその話はしないでください。 Commented Jul 4 at 9:54
  • 1
    @DavideBordoni Yes that sentence is correct, and it means the listener shouldn't bring up the その話 when eating (both before and while eating).
    – naruto
    Commented Jul 4 at 12:18
  • I see, thank you! Commented Jul 4 at 17:31

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