回複：這車能買嗎？好像外觀有點問題吧？但carfax似乎沒問題。

If Carfax says the car was involved in accident, then it was involved in accident.
If Carfax says the car has not been involved in accident, it MIGHT have been involved in accident, because sometimes if the accident isn't reported to police to DMV, then it isn't on record.
If you have doubt, ask your friends or someone who has experience to check it. Also ask seller if you can do a mechanical check.