PURPOSE: To quickly find out the execution time of a program even when the program is not executed by providing this program execution time calculating system with a means for obtaining execution frequency in a prescribed section and a means for calculating the execution time of the section concerned and calculating the whole execution time of the section concerned based upon the calculated execution time and its execution frequency.

CONSTITUTION: In the case of inputting a source program 2 to a compiler 1 and analyzing its syntax, an execution frequency input means 11 obtains execution frequency from a specification line for specifying the number of times of executing a fixed section in the program 2. An execution time calculating means 14 calculates the sum of execution time values of respective instruction strings formed by compiling the fixed section of the program 2, calculates the estimation value of the execution time of the fixed section concerned by multiplying the execution frequency by the sum of execution time values and totalizes the execution time values of all sections in the program to find out the whole execution time of the program. Consequently the execution time of the program can be quickly found out without practically executing the program.