An atmosphere-opening structure is provided for a canister of a vehicle which can prevent invasion of dust and water drops from an atmosphere-opening passage by a simple configuration which is easy to produce. A fuel tray is provided around a fuel filler such that fuel leaking from the fuel filler to the outside upon refueling is received by the fuel tray. The fuel tray is covered with a fuel lid which can open and close the fuel filler from above. A drain hole for discharging fuel to the outside is provided in the fuel tray. An opening hose for communicating the canister and the atmosphere with each other is provided. An opening end of the opening hose is communicated with a position higher than the drain hole in the fuel tray.