An arithmetic program conversion apparatus, an arithmetic program conversion program and an arithmetic program conversion method that can convert the floating-point arithmetic of an arithmetic program into a fixed-point arithmetic without degrading the accuracy. The apparatus comprises a profile section that uses as object variables the floating-point type variables of an arithmetic program for performing floating-point arithmetic operations, alters the arithmetic program so as to output the changes in the values of the object variables as history at the time of executing the arithmetic program in order to provide a first program, executes the first program and detects the range of value of the object variables according to the history obtained as a result of the execution and a conversion section that alters the arithmetic program according to the ranges of value of the object variables as detected by the profile section so as to convert the object variables into fixed-point type variables in order to provide a second program, executes the second program and determines if the accuracy of the outcome of the execution of the second program meets the predefined and required accuracy level or not.