PURPOSE: To improve the rigidity of a main body case and to prevent warpage and deformation by ultrasonic welding.

CONSTITUTION: The three peripheral side walls of upper and lower cases 1a and 1b constituting the main body case 1, that is, the back side walls 10a and 10b and the right and left side walls 11a, 11b, 12a and 12b are respectively ultrasonic-welded. However the front end areas 11a', 11b', 12a' and 12b' of the right and left side walls and the end faces of the right and left front side walls 9a and 9b of the upper and the lower cases 1a and 1b are not ultrasonic- welded. Then, the upper and the lower cases 1a and 1b are screwed by tapping screws 13 at corner parts on front right and left sides and center parts on front right and left sides. By screwing them, the change of the thrust clearance of a tape guide roller 4 is decreased and the positional deviation of a tape guide block 7 is prevented.