A therapeutic or prophylactic agent for leukemia is disclosed. The therapeutic or prophylactic agent comprises as an effective ingredient a glycine derivative having a specific structure or a pharmaceutically acceptable salt thereof, for example, the below-described compound [(E)-2-(2,6-dichlorobenzamido)-5-[4-(isopropyl-pyrimidin-2-ylamino)phenyl]pent-4-enoic acid]. The therapeutic or prophylactic agent for leukemia according to the present invention shows the excellent absorbability and in vivo stability when orally administered, and exhibits prominent therapeutic or prophylactic effects.