The filter includes a first case member (an upper case member), a second case member (a lower case member), and a filter medium with an end portion held between the first and second case members. The first and second case members include holding portions, respectively, for holding the end portion of the filter medium in a bent position and welded portions, respectively, which are spaced apart from the holding portions and are welded together by a laser beam. The holding portions include vertical press surfaces, respectively, for pressing an inner end portion of the filter medium in the joining direction P between the case members. The holding portions also include lateral press surfaces and, respectively, for pressing an outer end portion of the filter medium in a direction intersecting the joining direction.