PURPOSE: To quickly execute a processing in a host device by providing a command for updating numerical information such as a money amount inside E2 PROM, etc., in an IC card and enabling updating numerical information by means of a one-time command processing.

CONSTITUTION: In the information processing method in the IC card, a command message 10 adding the designition of an area in a non-volatile memory where rewriting is possible, the designition of an arithmetic processing in subtraction or addition and the disignition of change quantity being subtraction quantity or addition quantity is received from the host device and the arithmetic processing where numerical data being stored in the designated area is designated by change quantity is executed. When the result of the arithmetic processing is a negative value or exceeds a previously set numerical value, a response message 30 indicating it is returned to the host device and, when the result is the one except them, the area is updated to be the above result so that the updating command is processed so as to return the response message 20 adding the above result to the host device.