Abstract: In a computer program having a plurality of functional modules, an operational time for a functional module must be sometimes measured by tracing of the process, to improve the program. In this case, start and end points of the module to be traced are set as measuring points, with the addresses thereof, and the instructions in each of the measuring points are replaced by for the time measuring instruction before tracing. When the tracing starts, the control is stopped by the time measuring instruction and a measuring of the time, exchange of the time measuring instruction for the original instruction, execution of the operation by the original instruction, and exchange of the original instruction for the time measuring instruction are carried out, in this order, and are repeated until the end of the process. After the end of the process, an accumulation of the time and operation times of the module having the same address are carried out and the accumulated time and operation times are output for each module.