TOKYO—Japan on Tuesday took a major step toward legalizing casino gambling, an unpopular gambit in the country that is favored by U.S. casino companies and by Prime Minister Shinzo Abe, who hopes it will boost tourism.

Parliament’s lower house on Tuesday passed a bill opening the way for casinos and sent it to the upper house for review. Mr. Abe’s Liberal Democratic Party, which controls the two chambers with a smaller coalition partner, said it hoped to enact the bill before the current parliament session ends next week.

The bill wouldn’t legalize casinos immediately. It calls on regulators to develop specific plans on issues such as licensing operators and preventing gambling addicts from using the casinos. Parliament would then need to approve final legislation for legalization before casino companies could develop their properties, likely in joint ventures with Japanese companies.

Proponents say they hope casinos could open in the early 2020s after the 2020 Summer Olympics in Tokyo.

Japan prohibits casinos but permits gambling in other forms. Publicly licensed bodies run lotteries and betting facilities for horse racing. And millions of people play pachinko, a Japanese version of pinball, at privately run parlors. Pachinko winners can exchange prizes for cash at shops that operate in a legal gray area.