A parallelism-adjustable bonding machine includes a first chamber, a second chamber, a press-bonding unit, a carrier and plural parallelism-adjusting units. The first chamber is configured to connect to the second chamber, so as to define a closed space therebetween. The press-bonding unit is disposed within the first chamber, and the carrier is disposed within the second chamber. The press-bonding unit is disposed to face the carrier configured to press and bond substrates placed on the carrier. Each of the parallelism-adjusting units is disposed on the first chamber, and includes an adjustment shaft extending through the first chamber and connected to the press-bonding unit. The adjustment shaft includes an adjustment member located outside the first chamber and the closed space. A user is able to adjust a parallelism between the press-bonding unit and the carrier in an efficient and precise manner, from the adjustment member.