To provide a contactless type card reader/writer with which generation of electromagnetic waves is reduced.

The contactless-type card reader writer is equipped with a transmitting antenna for transmitting an electromagnetic wave to an IC card and a receiving antenna for receiving an electromagnetic wave from the IC card and sends and receives data to and from the IC card which is arranged at a distance. The transmitting antenna is driven with low electric power and the approach of the IC card to the transmitting antenna is detected by the impedance variation of the transmitting antenna which is caused, when the IC card enters an area close to the card/reader writer. After the IC card is detected, the low electric power is switched to a higher level to drive the transmitting antenna, which is so controlled as to send and receive data to and from the IC card.