1. An automatic program conversion method for making a program running in one environment executable in other environments, said conversion method comprising: where at least one pair of a first instruction pattern information element representing an instruction pattern in an old source program and a second instruction pattern information element representing an instruction pattern in a new source program is stored in a memory part, an analysis step of analyzing, using an analysis means, a number of times that said first instruction pattern information element appears in said old source program; an analysis results output step of outputting, using an output means, analysis results obtained in said analysis step; an instruction pattern conversion step of converting, using a conversion means, descriptions in said old source program that correspond to said first instruction pattern information element analyzed, in said analysis step, as appearing a predetermined number of times or more, so as to correspond to said second instruction pattern information element that is paired with said first instruction pattern information element appearing said predetermined number of times or more; a new program output step of outputting, using an output means, a new source program resulting from said old source program having been converted in said instruction pattern conversion step; and an input receiving step of receiving input, manually entered by a user using an input means, regarding descriptions in said old source program that correspond to said first instruction pattern information element analyzed, in said analysis step, as appearing less than said predetermined number of times, so that said descriptions will be modified for said new source program.