Transactions in the cyberspace reached a new monthly high of 10.04 trillion won in October, up 36 percent from a year earlier, according to Statistics Korea.
The double-digit growth came as the number of business days increased to 25 days in the month from 20 days in the same month of last year, raising the possible days for delivery.
The traditional Chuseok holiday, a South Korean version of Thanksgiving Day, moved to September this year from October last year.
Demand was strong for winter clothing ahead of the winter season, which the weather agency forecast to be one of the country's coldest seasons.
Clothing transactions in the cyberspace surged 38.5 percent in October from a year earlier, with those for electronic and telecommunication devices jumping 38.2 percent on demand for air purifier and clothes dryer.
Demand for food delivery services soared 49.8 percent amid the rising number of one-person households.
Among the total online shopping, the mobile shopping through smartphones picked up 43.8 percent over the year to 6.24 trillion won (5.6 billion U.S. dollars) in October.
It was the biggest monthly figure since the relevant data began to be compiled in January 2001.