PROBLEM TO BE SOLVED: To provide methods that enable stable production of antitumor agents in view of quality and production quantity.SOLUTION: The invention provides an antitumor agent containing a composition having an antitumor activity, which composition comprises a fraction of a resultant substance obtained by processing a sugar with heat. The invention provides a foodstuff containing a composition having an antitumor activity, which composition comprises a fraction of a resultant substance obtained by processing a sugar with heat. The invention also provides a medicine containing a composition having antitumor activity, which composition comprises a resultant substance obtained by treating a sugars with heat or a fraction thereof.SELECTED DRAWING: Figure 1