To provide a vehicle driving key system applied when a vehicle utilizes a key-depositing type car pool and capable of transferring a driving license function of a driver's license.

A vehicle driving key system comprises a user's side IC card for storing data of a driver's license as ID data and a CPU 101 for outputting a signal allowing an driving of the vehicle by collating registration data stored in advance in a memory 103 to ID data of the user's side IC card. Driving of a vehicle is allowed only when an driving allowing signal is outputted from the CPU 101. In addition, there are provided an IC card reader 204 for reading the ID data, a CPU 201 for controlling an driving allowing function stored in the user's side IC card, and MODEMs 105, 205 for transmitting electronic data between CPU 101 and CPU 201. When a signal for instructing a transferring of driving allowing function given by a user is acknowledged by an input terminal 206 at CPU 201, the ID data of a car pool manager side IC card is stored in the memory 103 of the CPU 101 as the registration data.