To provide a security system capable of improving security as compared with a conventional system.

A security system 1 comprises: a random number generator 2 provided in a vehicle; a mobile phone 3 having a camera function for taking a picture of a random number which is generated by the random number generator 2 and displayed on the generator 2; and a management center 4 that analyses transmitted information from the mobile phone 3 and reflects the analysed results for vehicle control. The management center 4 issues an unlocking command of a door lock when the random number which is obtained through the mobile phone 3 matches a reference random number.