1. An emulation method, comprising the steps of: creating beforehand an individual emulation coding, a collective emulation coding, and an instruction combination history table for denoting a relationship between a combination of a plurality of target instructions processed collectively and information denoting a branch destination of said collective emulation coding; fetching, via a programmed processor, from a memory and decoding a plurality of target instructions which are called as current instructions hereafter; and prior to the fetching from a memory the next target instruction to said current instructions, determining via a programmed processor whether or not it is possible to execute collective emulation for said current instructions based on the combination of said current instructions, and upon said determination being affirmative, branching to coding which is created in a memory beforehand, thereby executing said collective processing emulation according to said coding.