Effective component generation device includes internal component and case. Internal components include discharger that generates an effective component. Case is formed in a box shape having discharge port through which an effective component is discharged, and houses internal components. Case includes metal body including a bottom plate and peripheral walls surrounding at least discharger in internal component. Metal body has seamless portion at a corner portion between two surfaces of adjacent peripheral walls oriented in different directions. As a result, there is provided effective component generation device capable of suppressing electromagnetic noise radiated to the outside of case and reducing an influence of electromagnetic noise to the outside.