In a multithread processor capable of executing a plurality of threads, in order to select a thread and instruction for increasing a throughput of the multithread processor, an instruction-issuance controlling device included in the multithread processor includes a resource management unit configured to manage stall information indicating whether or not each of threads in execution is in a stalled state; a thread selection unit configured to select a thread which is not in the stalled state among the threads in execution; and an instruction-issuance controlling unit configured to perform controlling so that simultaneously issuable instructions are issued from among the selected thread.