A fluid filter including: an upper case member having a flow outlet; a lower case member having a flow inlet; a filter element having a folded filter material and a holding frame which holds the circumferential part of the filter material and is sandwiched between the upper case member and the lower case member; and a reinforcing member provided to extend in a direction crossing the ridge line direction of the folds of the filter material, the reinforcing member is provided in such a manner that, when the height of the folds is defined as h1, the lower end thereof is positioned above a position of 0.6 h1 from the upper end of the folds.