A development agent supply device includes a casing having an opening and a development agent storage section, a development agent holding member housed in the casing such that a development agent holding surface thereof faces a developer-supplied device via the opening, a first electric-field transfer board that transfers development agent with a traveling-wave electric field along a down-facing development agent transfer surface in a predetermined direction from the development agent storage section to the opening and faces the development agent holding surface at a downstream end in the predetermined direction, and a second electric-field transfer board that includes a first section facing an downstream end of the first electric-field transfer board in the predetermined direction, and a second section facing the development agent holding member and transfers development agent received from the first electric transfer board at the first section, to the second section with a traveling-wave electric field.