1. A performance evaluation simulation apparatus that evaluates performance by performing a simulation on a software model and a hardware model in which a process to be performed is provisionally determined by using software and hardware from specifications of a system, the performance evaluation simulation apparatus comprising: a processor including a basic-process-unit dividing unit that divides the process into basic process units, which are execution units of the process to be performed in the software model based on an execution log that represents execution history obtained by executing the software model on an actual machine or simulation software; a throughput calculating unit that calculates a throughput of each of the basic process units obtained through division by the basic-process-unit dividing unit, from the number of instruction address strings or the number of address strings for data access kept in the execution log; an arrangement-structure changing unit that compares each throughput calculated by the throughput calculating unit and a predetermined threshold and changes an arrangement structure so that a basic process unit with a throughput exceeding the predetermined threshold is changed from the software model to the hardware model; a statistical-information generating unit that generates statistical information on which performance evaluation is based by performing a performance evaluation simulation on the basic process unit whose arrangement structure has been changed by the arrangement-structure changing unit to the hardware model and basic process units arranged in the software model, the performance evaluation simulation executing a bus access via an instruction cache and a data cache, to measure data required for operation analysis of the system; and a determination-condition setting unit that sets a target processor load factor or a bus occupancy by the target processor for determining the performance evaluation result of the target processor on which the performance evaluation simulation is to be performed, wherein the arrangement-structure changing unit, when the statistical information obtained after the performance evaluation simulation is performed does not satisfy the target processor load factor or the bus occupancy by the target processor set by the determination-condition setting unit, changes the predetermined threshold, compares the throughput calculated by the throughput calculating unit and the changed predetermined threshold, and changes an arrangement structure so that a basic process unit with a throughput exceeding the predetermined threshold is changed from the software model to the hardware model.