The present invention provides an alignment device of cutting machine, which includes: a stand and a ball transfer unit mounted on the stand. The ball transfer unit includes a main body, a first rotating body, and a plurality of second rotating bodies arranged between the main body and the first rotating body. The main body has an end forming a receiving chamber and thus forming a receiving chamber sidewall. The second rotating bodies are rotatably arranged on the receiving chamber sidewall. The main body forms an air entrance passage in communication with the receiving chamber. The receiving chamber sidewall extends out to form a bearing section corresponding to the air entrance passage. The bearing section has a side surface in which air outlet ports are formed. The main body has an opposite end forming a connection section that is mateable and coupleable to the stand. The present invention uses a ball transfer unit to replace the float pad made of porous carbon fiber material for aligning a glass substrate in order to achieve the purposes of lowering down cost.