Disclosed is an anti-cancer agent which can inhibit the progression of cell cycle in the M phase, unlike taxane anti-cancer agents. The anti-cancer agent comprises a compound capable of inhibiting specifically the expression and/or functions of RBM8A depicted in SEQ ID NO: 1, Magoh depicted in SEQ ID NO: 3 or an isoform thereof. The anti-cancer agent can inhibit the expression and/or functions of RBM8A or Magoh in cancer cells to terminate the cell cycle in the M phase, thereby inhibiting the proliferation of the cells. Therefore, the anti-cancer agent can inhibit the proliferation of cancer cells and induce the apoptosis of cancer cells, leading to the cure of cancer.