Ic card reader/writer and ic card transactions processing apparatus capable of producing various frequency clock pulses

An IC card reader/writer (5) has frequency mode identifying means (22) for determining whether or not an IC card (23) loaded thereon has an identifiable frequency. When the frequency mode of the IC card (23) is identifiable, clock frequency determining means (22) reads frequency data representative of an operating clock frequency out of the IC card (23) to determine an operating clock frequency particular to the card (23). Based on the determined operating clock frequency of the IC card (23), frequency setting means (25, 26, 27) converts reference clock pulses being generated by reference clock generating means (21, 32) into clock pulses which match the clock frequency of the IC card (23), and feeds those clock pulses to the card (23). The reader/writer (5) is capable of producing clock pulses the frequency of which is variable in matching relation to the frequency of operating clock pulses of an IC card.