A fluid filter, which is adapted for separating a less dense fluid floating on a high dense fluid, includes at least a fluid filtering arrangement including a floating wing adapted for floating on the less dense fluid and at least a fluid outlet formed on the floating wing, and a container body, which is extended from the floating wing, having a fluid collecting cavity communicating with the fluid outlet, wherein the fluid outlet is formed at a position above the fluid collecting cavity. Therefore, when a downward force is applied on the floating wing until the fluid outlet is slightly positioned below a surface level of the less dense fluid, the less dense fluid is allowed to flow into the fluid collecting cavity through the fluid outlet by gravity.