The RFID system includes an RFID reader for sending information selected from among collision type information, idle type information, and readable type information, to all of the RFID tags depending on the number of signals in the corresponding time slot, and RFID tags for performing functions, in which, when information, indicating that a current time slot is a collision type, is fed back from the RFID reader, each of RFID tags selects one arbitrary value of either 0 or 1 and is assigned a time slot, in which a corresponding RFID tag will send a signal to the RFID reader, based on the selected value, a single tag group that caused a collision is divided into two sub-groups depending on the assigned time slots, and tags of the sub-groups send signals, including IDs thereof, to the RFID reader in different time slots for the respective sub-groups.