Abstract: Provided is an auxiliary sun visor for headgear in which the auxiliary sun visor is easily installed in headgear to thereby intercept sunlight over the whole surface of user's neck section as well as user's face, and thus discharge hot air generated from the neighborhood of the face and neck smoothly to the outside. The auxiliary sun visor includes: a sunshade portion which is detachably coupled with an adhesive female portion and an adhesive male portion in which a fitting hole through which the headgear is fitted is formed in the inner central portion of the sunshade portion; a ventilation net which is pendently formed so that air smoothly flows to the edge of the sunshade portion; and left and right screen curtains and rear neck screen curtains all or part of which are separately formed at the state of being spaced from each other by cutoff regions.