An obfuscation device includes a first instruction generating unit, for each of a first process and a second process, which generates an initialization instruction for securing a management area for managing identification information indicating an instruction block that should be executed next so as to proceed with the process. Further, a second instruction generating unit generates a selection instruction (i) to make a first selection selecting a process that should be proceeded out of the first process and the second process, (ii) to make a second selection selecting an instruction block indicated by the identification information managed in the management area as an instruction block that should be executed for proceeding with the process selected by the first selection, and (iii) to cause the execution device to execute the instruction block selected by the second selection, and stores the selection instruction in a storage unit.