A semiconductor memory device includes: a temperature sensor configured to sense an internal temperature of the semiconductor memory device and generate a temperature signal; and a temperature code storage unit configured to receive the temperature signal in response to a temperature code write control signal that is generated when an operation corresponding to a specific command is performed, generate an operating temperature code corresponding to the temperature signal, compare the operating temperature code with a previously stored temperature code, store a larger temperature code of the operating temperature code and the previously stored temperature code as a maximum temperature code, and output the maximum temperature code to an external source in response to a temperature code read control signal.