A non-volatile storage device of the present disclosure includes non-volatile memory configured to have a plurality of areas for storing data, and a memory controller configured to write the data to the non-volatile memory and to read the data from the non-volatile memory. The memory controller includes a memory interface (I/F) connected to the non-volatile memory, a threshold calculator calculating a threshold for the number of error bits of the data based on a storage condition in the case of storing the data in the non-volatile memory without power, and a refresh controller determining whether refresh processing of the data is necessary, based on the threshold and the number of error bits of the data, and executing the refresh processing of the data if the refresh processing of the data is necessary.