To provide a miniaturizable filter in which a holding frame and a case member of a filter element are firmly joinable by a laser welding.

The filter 1 includes a first case member (bottom case 2), a second case member made of resin (top case 3) and a filter element 8 having a filter medium 6 and a holding frame 7 made of resin holding the peripheral end of the filter medium. The holding frame is held between holding parts 10 and 13 prepared in each of the first and second case members, and possesses a plurality of holding frame side projections 20a, 20b projecting in a holding direction P1 and placed by being shifted in a direction P2 intersecting the holding direction. The holding part of the second case member possesses a plurality of case side projections 21a, 21b projecting in a holding direction and placed by being shifted in a direction P2 intersecting the intersecting direction. The plurality of holding frame side projections and the case side projections are respectively brought in contact with each other on a plane along the holding direction, and laser welded parts w1 and w2 are formed at the contact points.

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