To prepare the coil of a data carrier in favor of sizes.

Adjustment capacitors 13a and 13b (13c and 13d) for adjusting a capacity value corresponding to the inductance value of an antenna coil 12 operating tuned to a prescribed operation frequency are formed in the shape of a comb at a prescribed position on a board 14 to eliminate inconvenience that the inductance value of the antenna coil 12 is determined simply according to the capacity value of a capacitor prepared in an integrated circuit 11 provided at the data carrier, thereby the coil 12 of the data carrier can be prepared in favor of the sizes and can simply be adjusted corresponding to the operation frequency.