The present invention provides an anti-plant virus agent which exhibits preventative and therapeutic effects on plant virus diseases. The anti-plant virus agent of the present invention is characterized by containing at least one compound selected from the group consisting of ascorbic acid derivatives represented by Formula (I) (wherein, R 1 to R 4 each independently represents a hydrogen atom, -SO 3 H -PO 3 H 2 , a glycosyl group, or -COR 11 , wherein R 11 represents an unsubstituted or substituted C1-30 alkyl group, or an unsubstituted or substituted C2-30 alkenyl group, with the proviso that R 1 to R 4 may not all be hydrogen atoms at the same time), and salts thereof.
