Researchers at University of Wroclaw in Poland who carried out the experiment believe the seasonal variation may have an impact on mate choice and on levels of adultery.
There is no clear explanation for the variation, but the researchers say one theory is that fewer female bodies are on display in the winter, so the rarity makes them more attractive.
The study has been published in the journal Perception.
The researchers also tested how attractive the men in the study found their own partner. The results showed the same seasonal pattern, with a peak in autumn and winter. But when the men were asked to rate their own attractiveness, there was no seasonal variation.