A biometric authentication system 10 includes an IC card 100 including a reading unit 110 sending generation information back to a terminal and a writing unit 111 writing biometric information in a storage area indicated in a write instruction, and a terminal 200 including a card generation acquisition unit 210 receiving from the IC card the generation information, a device generation acquisition unit 211 receiving from a biometric authentication device the generation information, a biometric information acquisition unit 212 receiving biometric information from the biometric authentication device 300, a first write instruction unit 213 identifying a storage area of the same generation as the generation of the biometric authentication device and transmitting a write instruction of the biometric information to the IC card, and a second write instruction unit 214 transmitting a write instruction for a storage area of the oldest generation to the IC card.