The present invention relates to an ethane-sulfonate salt of N-{5-[(6,7-dimethoxy-4-quinolinyl)oxy]-2-pyridinyl}-2,5-dioxo-1-phenyl-1,2,5,6,7,8-hexahydro-3-quinolinecarboxamide, which has an Axl-inhibiting activity and is useful as a prophylactic and/or therapeutic agent for immune diseases, cancer and the like, a crystal thereof, and a pharmaceutical composition thereof.