1. A thread debugging device for debugging at least one thread among a plurality of threads which are executed in association with each other on a computer, comprising: target thread execution means for causing the computer to execute at least some processing of at least one target thread to be debugged among the plurality of threads; and non-target thread execution means for causing the computer to execute non-target threads, which are threads other than the at least one target thread among the plurality of threads, during execution of the at least one target thread by the target thread execution means while restricting access by the non-target threads to at least some hardware resources of the computer.