A non-contact IC tag system includes a plurality of non-contact IC tags, each of which includes identification information and a memory for storing a predetermined amount of data; and a reader/writer that sends an operation command via radio to each of the non-contact IC tags. The non-contact IC tags include a plurality of slave IC tags and a master IC tag. The master IC tag holds memory configuration information that is used when building a memory space with a memory area of the memory of each of the slave IC tags and a memory area of the memory of the master IC tag.