The present disclosure 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, R1 to R4 each independently represents a hydrogen atom, -S03H, -P03H2. A glycosyl group, or -COR11, wherein R11 represents an unsubstituted or substituted C1-30 alkyl group, or an unsubstituted or substituted C2-30 alkenyl group, with the proviso that R1 to R4 may not all be hydrogen atoms at the same time), and salts thereof.
