The present invention provides a compiler that can compile Java byte code at high speed while employing only limited resources. The technique converts byte code into intermediate code that employs, as an opcode, an address of an execution routine that corresponds to a byte code, and executes the execution routines in a sequential order corresponding to that of the intermediate code. The length of the intermediate code is constant and the bit location of the opcode is also constant. The execution routine is stored in sequential areas in a memory, and an offset of the execution routine group from the head address of the sequential memory area is employed as an opcode. Furthermore, by employing empty pipelines in the CPU, one part (operand generation and a jump) of an instruction group for jumping to the next intermediate code execution routine, and one part (prefetching of intermediate code and address calculation of a execution routine) of an instruction group for jumping to the next plus one intermediate execution routine can be executed in parallel to the original intermediate code process. Further, rule-based optimization using idioms is performed, without requiring analysis of the program structure.