The hydrogen peroxide manufacturing device according to an embodiment is provided with: an ejector unit having an introduction-side expanded diameter part into which water to be treated is introduced, a nozzle unit which is provided in continuation from the introduction-side expanded diameter part and which has, provided on the side wall thereof, an introduction opening into which a raw material gas containing oxygen gas is introduced from the exterior, and a discharge-side expanded diameter part which is provided in continuation from the nozzle unit and through which water to be treated, with which the raw material gas has been mixed, is discharged; and an electrolysis unit provided on the downstream side of the ejector unit, the electrolysis unit being provided with electrolysis electrodes for electrolyzing the water to be treated with which the raw material gas has been mixed, which has been discharged, and generating hydrogen peroxide gas using the raw material gas as a raw material. The hydrogen peroxide manufacturing device can therefore continuously manufacture hydrogen peroxide water without using hydrogen peroxide serving as a reagent.