A method for allowing production of high-purity perrhenic acid from crude rhenium sulfide by applying a dry process is provided. A method for producing an aqueous solution of perrhenic acid includes 1) a step for roasting rhenium sulfide under an oxygen-containing gas to collect gasified rhenium oxide; 2) a step for cooling and solidifying the gasified rhenium oxide while keeping sulfur oxide entrained in the gasified rhenium oxide a gaseous state, and subsequently performing solid-gas separation, thereby improving purity of rhenium oxide; and 3) a step for dissolving the solidified rhenium oxide into water, or heating and gasifying the solidified rhenium oxide and then dissolving the gasified rhenium oxide into water, to obtain the aqueous solution of perrhenic acid.