In a security system, a security control apparatus 300 includes an authentication processing unit 31 for perform an authentication on whether the mobile terminal is a permitted terminal, a distance determining unit 32 for determining whether the mobile terminal is located within a predetermined distance from a printer 100, and an unlocking unit 33 for transmitting an unlock instruction signal to the printer 100 when the authentication is successful and it is determined that the mobile terminal is located within the predetermined distance from the printer 100. Therefore, a locking mechanism of the printer 100 cannot be unlocked even if the authentication is successful, and the locking mechanism of the printer 100 can be unlocked when it is further determined the mobile terminal is located within the predetermined distance from the printer 100.