The present filter 1A comprises a first case member(an upper case member) 2 and a second case member (a lower case member) 3 that are made of synthetic resin and are mutually joined to form a filter chamber S, and a filter element 4 including a filtering medium 5 and a holding frame 6 that is made of synthetic resin, holds a peripheral portion of the filtering medium 5 and is held between joining ends 2b and 3b of the case members 2 and 3, and weld portions w1 and w2 formed by laser light are provided at a contact area extending in a joining direction between the holding frame 6 of the filter element 4 and at least one joining end of the joining ends 2b and 3b of the case members 2 and 3.