To perform management of complicated attendance information, simplification of editing of the attendance information, and reduction of a lot of labor.

This attendance management system using a cellphone with a built-in IC card 101 has: a built-in IC card 101A for storing an employee number, displaying an operation screen for attendance management on a display part of the cellphone with the built-in IC card, storing an attendance state selected, input and edited on the displayed operation screen, and a selected and input seat leaving state, and built in the cellphone with the built-in IC card; an IC card reader 102 for performing transmission/reception to the built-in IC card when the cellphone with the built-in IC card is held up when coming to an office or when leaving the office, receiving the employee number, the attendance state, and the seat leaving state from the built-in IC card, transmitting a received date to the built-in IC card as an attendance time, and storing the transmitted attendance time into the built-in IC card together with the attendance state; and a database 103 for receiving the employee number, the attendance state, the attendance time, and the seat leaving state from the IC card reader, storing them, and transmitting the seat leaving state to the cellphone with the built-in IC card on demand.