A hard/soft cooperative verifying simulator is based on a SystemC simulator, and provides the capability of reducing overhead of context switching control thereby to shorten processing time. Time keepers for controlling simulation times of a plurality of threads are provided corresponding to the threads generated as simulation models for hardware and software. Each of the time keepers has a variable which holds a simulation time for each thread, a variable which holds a summation time, and a break request queue which stores a break time and its corresponding break method therein. The time keeper manages both variables and the queue in response to six types of method invocations from the thread, and invokes a wait function of the SystemC simulator when necessary. It is thus possible to reduce the number of times that a wait function invocation is performed, and shorten the entire processing time.