A mobile device includes a memory for storing therein a subroutine management table to manage kinds of existing codes out of native code, first code and second code for a plurality of subroutines contained in content, a virtual machine, a precompile circuit for producing second code from first code and a subroutine management circuit for changing over processing in accordance with the kind of existing code for subroutine called up during execution of content. The subroutine management circuit judges kind of existing code with reference to the subroutine management table when the processing is changed over.