A fluid filter including: an upper case provided with an outlet hole; a lower case provided with an inlet hole; and a filter element held between the upper case and lower case, wherein the outlet hole and the inlet hole are arranged opposite to each other. The filter element includes a first filter material which is folded and arranged in a communication part connecting the outlet hole and the inlet hole, and a second filter material which is folded and spaced apart from the communication part, and the retention interval L1 of the first filter material in the fold line direction is smaller than the retention interval L2 of the second filter material in the fold line direction.