1. A program conversion method comprising: compiling a program and generating a machine code by controlling a computer when an execution object of said program transitions execution from a first code column executed by means of an interpreter to a second compiled code column, including: a first step of setting a first code that is ignorable in a predetermined transformation for the second code column among codes in the first code column, which affects transformation of the second code column and storing the first code into memory; and a second step of performing said predetermined transformation for said second code column by ignoring said first code on the basis of said first code stored in the memory, wherein said second step comprises two sub-steps of: (i) a first sub-step of determining whether a copy instruction can be propagated across a junction of said first code column and said second code column for each of the codes in consideration of a variable included in the first code ignorable in the predetermined transformation of said second code column; and (ii) a second sub-step of performing a transformation of said second code column including propagation of the copy instruction the basis of the step of determining; and a third step of generating a compensating code required for transforming the second code column including propagation of a copy instruction, and inserting the code into said first code column prior to the transformation of said second code column, wherein the transformation including said propagation of copy instruction is performed for said second code column by ignoring said ignorable first code in said second step.