As noted on this website, New Chitose Airport is the main airport for people in Sapporo. Okadama airport is also in Sapporo, but this airport is small and mainly used for flights inside the prefecture.
New Chitose Airport has both domestic and international airlines. Thus some foreigners can visit Hokkaido directly. This airport has many domestic flights. Especially, the flights to Tokyo are so frequent and the number of passengers used to be the most in the world. Nowadays, some LCC began to have flights to Tokyo and costs of them are inexpensive.
I have many occasions to visit this airport and I like visiting there because I can enjoy shopping, foods and some event whenever I go there. Sometimes I can get some foods like cookies and chocolates for free.