A thread debugging device which can provide reliable debugging is provided when at least one thread is debugged among a plurality of threads which are executed in association with each other. According to the thread debugging device, a target computer (20) executes at least some processing of at least one target thread to be debugged among the plurality of threads, and further executes 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 while restricting access by the non-target threads to at least some hardware resources of the computer (20).