An assembled air cleaner includes an air blowing box, a plurality of first filter boxes that is stacked in a vertical direction and disposed above the air blowing box, and an air inlet box disposed on top of the topmost first filter box. At least one filter is provided inside the first filter boxes. Each first filter box has a bottom wall and a flange protruding upwardly around a peripheral edge of the bottom wall. The flange is configured to hold against a bottom of the filter in an airtight manner. A plurality of airtight members is provided on each first filter box and can be pressed against the filter, thereby improving filtering and dust collection effects greatly.