To provide an IC card reader/writer which can access an IC card at the optimum speed, without resetting the clock supply sequential position of the IC card having a prescribed clock.

When IC card processing is shifted into a first sort IC card which is active for a first clock into a second sort IC card which is active for a second clock, sensing order parameters can be automatically changed into the second sort IC card in accordance with the number of accessed first sort IC cards. For this reason, reconfiguring of the clock supply sequential setting is not required, after the IC card processing has shifted into the first sort IC card into the second sort IC card. Therefore decline in the processing efficiency of the IC card reader/writer is prevented, access with optimum speed to the IC card is available, and processing capability of the IC card reader/writer is improved.