The invention provides a mask fixing device and a mask fixing method used in a lithography machine. A mask is adsorbed by matching a flexible mechanism with an electromagnetic method; the control is simple; the adsorption and the separation can be controlled only through switching current; and by using the device and the method, no deformation in an adsorption process of the mask can be guaranteed, and the requirement of high-accuracy positioning of the high-grade lithography machine is met. Meanwhile, a series of processing problems caused by vacuum gas leakage and the like are avoided, convenience and easiness in control are guaranteed, and the cost is saved.