TOKYO — SoftBank Group Corp. Chief Executive Masayoshi Son said Thursday that he is stepping down from the board of Chinese e-commerce giant Alibaba Group Holding Ltd., effective the same day.

Son’s announcement, which he made at the end of SoftBank’s 9984, -0.48% annual shareholder meeting, follows the resignation — also effective Thursday but announced last month — of Alibaba BABA, -1.10% co-founder Jack Ma from SoftBank’s board.