Provided are a memory controller for controlling a refresh cycle of a memory and a method thereof. In this method, a temperature measure command is generated to measure an operating temperature of the memory. Next, a measured temperature in response to the temperature measure command is received. Then, a temperature difference between the measured temperature and a reference temperature is detected if the measured temperature is different from the reference temperature to change the refresh cycle according to the temperature difference, and if the measured temperature is equal to the reference temperature the method returns to the temperature measure command generating step. Thereafter, a refresh command is applied to the memory in response to the changed refresh cycle.