There are provided a non-contact type semiconductor device, a mobile terminal device, and a communication system capable of suppressing unauthorized read, thereby assuring security. The non-contact type semiconductor device records information for identifying a read device of a communication destination and a request from a read device in a recording area. Moreover, the non-contact type semiconductor device holds authentication information and access authority, requests the read device to send authentication information, correlates the authentication information with the authentication information and access authority held, and executes the request from the read device according to the correlation result. Furthermore, by performing mutual communication by using the read device, the non-contact type semiconductor device, and a mobile terminal device using the non-contact type semiconductor device, it is possible to suppress unauthorized read, thereby assuring security.