A locking device for a tape cassette housing of a tape recorder comprises a locking recess and a locking protrusion respectively provided in sides of a tape cassette housing and a deck chassis and corresponding to each other, thereby fastening a tape cassette housing to the deck chassis, the tape cassette housing resiliently coming into contact with the deck chassis as a tape cassette is loaded. In here, around external circumference of the locking protrusion is formed at least one edge, and an end of the edge comes into contact with a corner of the locking recess right before the locking protrusion is inserted into the locking recess. Accordingly, the locking protrusion comes into linear contact with the corner of the locking recess in loading/unloading operations of the tape cassette so that the stopping of the ascending and descending movements of the tape cassette housing is prevented during the loading/unloading operations of the tape cassette.