A storage system includes a host and a storage apparatus. The host having multiple paths connecting with the storage apparatus transfers path identification information received from the storage apparatus, to the storage apparatus via all paths other than a path through which the path identification information has been transmitted. The storage apparatus includes a table for storing the path identification information transmitted to the host and path tables for storing the path identification information received from the host. When the storage apparatus receives a request for replacing the firmware, it determines whether the path tables are matched by comparing the path tables with each other. If the path tables are matched, the storage apparatus sequentially replaces the firmware corresponding to the multiple paths in a hot swapping manner.