A secure processor, comprising: an instruction execution unit for executing an execution code of a process in a memory; a secure process identifier generation unit for generating a secure process identifier when an instruction to generate the process is issued; a process information retention unit for retaining the secure process identifier and an authentication key for authentication of the execution code while the process is still present as information related to the process; a translation look aside buffer including a page table entry of a page storing the execution code, the secure process identifier read from the process information retention unit being set up in the page table entry when paging-in the execution code into the memory; an authentication unit for setting the secure page flag in the page table entry when the execution code corresponding to the process is successfully authenticated using the authentication key, after the execution code corresponding to the process is stored in an unused page in the memory and the secure process identifier corresponding to an address of the unused page is stored in the page table entry; a memory access control unit for comparing the secure process identifier stored in the page table entry, in which the corresponding secure page flag is set, with the secure process identifier which is retained in the process information retention unit, and for permitting the instruction execution unit to access the page in the memory where the execution code is stored and execute the execution code, if the secure process identifier retained by the process information retention unit matches with the secure process identifier set up in the page table entry. an instruction execution unit for executing an execution code of a process in a memory; a secure process identifier generation unit for generating a secure process identifier when an instruction to generate the process is issued; a process information retention unit for retaining the secure process identifier and an authentication key for authentication of the execution code while the process is still present as information related to the process; a translation look aside buffer including a page table entry of a page storing the execution code, the secure process identifier read from the process information retention unit being set up in the page table entry when paging-in the execution code into the memory; an authentication unit for setting the secure page flag in the page table entry when the execution code corresponding to the process is successfully authenticated using the authentication key, after the execution code corresponding to the process is stored in an unused page in the memory and the secure process identifier corresponding to an address of the unused page is stored in the page table entry; a memory access control unit for comparing the secure process identifier stored in the page table entry, in which the corresponding secure page flag is set, with the secure process identifier which is retained in the process information retention unit, and for permitting the instruction execution unit to access the page in the memory where the execution code is stored and execute the execution code, if the secure process identifier retained by the process information retention unit matches with the secure process identifier set up in the page table entry.