An air blower (14) is accommodated within a housing (2), and the front face of the air blower (14) is located on the front wall (6) side of the housing (2). A restraint member (20) provided within the housing (2) is in contact with the rear face of the air blower (14). An air blower cover (30) is mounted to an air blower mounting section (12) on the front wall (6) side of the housing (2) so as to face the air blower (14). Pressing members (48, 48, 50, 50) provided to the housing (2)-side surfaces of the air blower cover (30) press the front face of the air blower (14) toward the restraint member (20) while the air blower cover (30) is mounted to the air blower mounting section (12).