Request delivery device, request delivery method, and request delivery program

A load balancer includes: a request queue that stores a request scheduled to be transmitted to a server; a transmission unit that transmits a request read from the request queue to the server capable of processing the request; a reception unit that receives a completion message indicating that processing of the request is completed; and a completion list that stores the completion message, and the transmission unit discards a request for which the completion message is stored in the completion list without transmitting the request to the server, and transmits, to the server, a request for which the completion message is not stored in the completion list and stores the request again in the request queue.