Bacground: Tooth discoloration is the changing of tooth color due to by external, internal or both that can be treated by bleaching treatment. The chemical agent on the teeth whitening agent has negative effect on the teeth and mucose tissues, so there is a need to look for alternative/natural bleaching agent. Spinach contains oxalic acid that can be used as natural bleaching agent. Purpose: To evaluate the effectiveness of 100% of spinach extract, 100% of spinach extract and milk, and 10% of carbamide peroxide for tooth bleaching process. Methods: This study was in-vitro experimental laboratories. Twenty four premolar teeth were immersed in coffee solution for 12 days. Then, subjects were divided into following groups: 100% of spinach extract, 100% of spinach extract and milk, 10% of carbamide peroxide and aquades. The dE*ab was measured using spectrophotometer before and after immersed in the extract solution. The statistical analysis was done using paired t test and wilcoxon, kruskal-wallis test and post hoc test. Results: Paired t test showed significant difference (p<0,05) in karbamid peroxide 10% group (p=0,038) and spinach extract 100% group (p=0,046). Kruskal-Wallis test showed significanct difference (p=0.014, p value < 0,05) in at least one of the groups. Conclusion: There is a difference effectiveness of teeth whitening process between 100% of spinach extract, 100% of spinach extract and milk, and 10% carbamide peroxide.