Grape seeds (Vitis vinifera L.) are known to be one part of the grapes that have potential as a good source of antioxidant activity that have not been optimally used. This research is designed to study effect of heating temperature and time towards antioxidant activity of grape seeds. Grape seeds were extracted using maceration method with acetone:water (70:30) at 45 °C for two hours. In research stage 1, the highest antioxidant activity was searched between the normal grape seeds and defatted grape seeds. Defatted grape seeds showed the best antioxidant activity, total phenolics, and total flavonoids which are 179.05 mg/L, 5.72 mg TAE/g extract, and 0.39 mg QE/g extract. Defatted grape seeds then heated at four different temperatures (50 °C, 100 °C, 150 °C, and 200 °C) at three different times (15 minutes, 45 minutes, and 75 minutes). The maximum antioxidant activity and total phenolics were achieved when the grape seeds were heated at 150 °C for 45 minutes. The best grape seeds extract had IC50 6.53 mg/L and phenolic content 6.59 mg TAE/g extract. While the highest total flavonoids was achieved when the grape seeds were heated at 150 °C for 75 minutes which is 2.57 mg QE/g extract.