A biphenyl compound having LSD1 inhibitory activity represented by the general formula (I) wherein ring A, ring B, R1 to R6, l, m, and n have the same meaning as defined in the specification, or a biphenyl compound thereof An antitumor agent administered in combination with a salt and another antitumor agent.一般式(I)[式中、環A、環B、R1~R6、l、m、nは明細書中で定義した通りの意味を有する]で表されるLSD1阻害活性を有するビフェニル化合物又はその塩と、他の抗腫瘍剤を併用投与する抗腫瘍剤。