Guide device with mechanism capable of minimizing damage to toner image by water droplet and image forming apparatus incorporating same

A guide device for guiding a recording medium discharged from a fixing device includes a first conveyance wall plate and at least one rib assembly mounted on the first conveyance wall plate. The at least one rib assembly includes a plurality of primary ribs contacting the first conveyance wall plate, each having a first thickness in a recording medium conveyance direction; and a plurality of secondary ribs mounted on selected ones of the plurality of primary ribs. Each secondary rib includes a bottom contacting the primary rib and having a second thickness in the recording medium conveyance direction that is smaller than the first thickness of the primary rib; and a top contacting the recording medium and having a third thickness in the recording medium conveyance direction that is smaller than the second thickness of the bottom of the secondary rib.