Partial refresh information indicating enabling/disabling of a refresh operation is set according to an external input and is output as a partial set signal. A refresh request signal is output periodically corresponding to a memory block for which a refresh operation is enabled. The partial set signal is masked so as to enable a refresh operation for all of the memory blocks during a period in which the partial refresh information is changed by the external input. Thus, it is possible to prevent disabling of a refresh operation in response to a refresh request even when timing of changing the partial refresh information and timing of occurrence of the refresh request signal overlap. Consequently, the refresh operation can be executed securely, and malfunctioning of the semiconductor memory can be prevented.