Mobile terminal in which plural sim can be installed and method of sim selection thereof

A method of selecting a subscriber identity module (SIM) in a portable terminal on which multiple SIMs are capable of being mounted, includes: a process of determining whether an application/service which is currently being executed is an application or a service for which security is previously set; and a process of selecting a SIM which is previously set for security use or a SIM which is set for general use according to a result of the determination, and performing communications.