To obtain an antifungal agent having a strong antifungal effect against the fungus causing candidiasis and excellent in safety by using a specific acid and/or its derivative as an active ingredient.

This antifungal agent is obtained by using kojic acid and/or its derivative. The antifungal agent shows a specifically strong antifungal effect against Candida albicans. A pure product of the kojic acid (5-oxy-2-oxymethyl-γ- pyrrone), a fermented liquid consisting essentially of the kojic acid obtained by fermenting a well-known strain having an ability for producing the kojic acid, a condensed liquid of the fermented liquid and the one obtained by extracting and crystallizing the kojic acid from the fermented liquid, are used as the active ingredient. The antifungal agent is administered by an oral dose or a direct topical application to a skin in a form of an oral medicine (a capsule, a tablet, etc.) or a medicine for external use (an ointment, etc.). The daily dose of the active ingredient is 1-10g as the oral dose and the active ingredient is used in 0.001-10wt.% concentration based on the whole medicament as the external use.