Floral gender of angiosperm often varies within and among populations. Not only plant size and pollination situation but also herbivorous damage may influence floral gender. We test the hypothesis that pre-dispersal seed predation affects the floral gender of andromonoecious herb, Peucedanum multivittatum. We compared plant size, male and hermaphrodite flower production, fruit set, and seed predation damage among 9 populations in the alpine meadows. Both male and hermaphrodite flower production increased with plant size but floral gender (proportion of male flowers) was independent of size. The number of male flowers increased at the early-snowmelt populations, while that of hermaphrodite flowers increased at the middle to late-snowmelt populations, resulting in the male-biased floral gender at the early-snowmelt populations. Pre-dispersal seed predation by micro-lepidopteran larvae was intense at the early-snowmelt populations because of the phenological matching between flowering period and appearance of predator moths. In contrast, predation damage was nothing at the late-snowmelt populations. There was a clear correlation between male flower production and the intensity of seed predation damage among populations. These results strongly indicate that the male-biased flower production is a strategy to maintain the reproductive success as a pollen donor under the condition of severe predation damage.