A storage apparatus has a plurality of storage media including each storage area in which a stripe is set extending over the storage area of the plurality of storage media. An access unit that writes a format data into the storage area, wherein when the plurality of storage media are formatted, the access unit writes an unformatted-state identifier indicating incompletion of formatting into at least a portion of storage area to be included in the stripe, or when the storage area to be included in the stripe is accessed for writing new data, the access unit reads out existing data stored in the storage area included in the stripe to be accessed. And when the unformatted-state identifier is detected from the existing data that has been read out, the access unit writes the new data or the format data to be written by formatting into the storage area.