Apparatus and method of providing platform independent secure domain

PURPOSE: A security environment device and a method thereof which is independent from platform are provided to switch into security environment by turning on security bit after succeeding branch command. CONSTITUTION: A security monitor(110) watches a call of a security code by a processor(100), and creates a branch instruction. If the branch instruction is successfully operated by the processor, the security monitor makes the security bit on. If the execution of the security code is completed, the security monitor makes the security bit off. A command bypass ROM(120) receives the branch instruction from the security monitor.