Cultivating a pluripotent stem cell in a medium comprising at least one member selected from the group consisting of ethanolamine, an ethanolamine analog, and a pharmaceutically acceptable salt thereof, and which is substantially free of β-mercaptoethanol or contains β-mercaptoethanol at a concentration of not more than 9 μM, and the like, is effective for the proliferation of a pluripotent stem cell while maintaining an undifferentiated state.