A method of controlling On-Die Termination (ODT) resistors of memory devices sharing signal lines is provided. The ODT controlling method comprises setting an ODT control enable signal of each of the memory devices and address/command or data termination information to a mode register of the corresponding memory device, and controlling resistances of ODT resistors of the signal lines in the memory devices in response to the address/command or data termination information and termination addresses. When only one of the memory devices is activated, ODT resistors of the activated memory device are set to a first resistance. When all the memory devices are activated, ODT resistors of the memory devices are set to a second resistance.