Abstract: A fuel cap capable of preventing a reduction in breathability in a housing due to a moistened adsorbent and appropriately discharging fuel vapor includes a housing including an inner space through which vapor generated in a fuel tank flows upward from below. A granular adsorbent is disposed in the inner space of the housing. A lower air-permeable layer is disposed below the adsorbent, and an upper air-permeable layer is disposed above the adsorbent. A lower porous member is disposed between the adsorbent and the lower air-permeable layer. The lower air-permeable layer, the lower porous member, and the upper air-permeable layer respectively have a porous structure. A density of the lower porous member is lower than a density of the lower air-permeable layer and a density of the upper air-permeable layer.