To provide an IC card, an IC card processing device, and its processing method capable of efficiently interpreting data.

Attribute data showing the attribute of application data is stored in the memory of the IC card while being associated with the application data. When reading the application data form the IC card, the associated attribute data is added to the application data and transmitted to an external device. When writing data onto the IC card, data transmitted from the external device is written into the memory while being associated with the attribute data stored in the memory of the IC card.