The objectives of this research were to study the effects of several thermal and biological processing methods on the polyphenol content and antioxidant acitivity of common bean seeds. Among thermal processing three soaking methods were used: (a) in water, 0,1% citric acid, and 0,07% sodium carbonate; all treatments in the temperature ranging from 100°C to 22°C, (b) cooking, (c) autoclaving (1at, 121°C) for 15 and 30 min, and (d) microwave treatment at 1300 and 2000 J/g. The latter processing methods were: (a) solid-state fermentation (using Rhizopus microsporus var. oligosporus sp-T3) and (b) germination (1-5 days). As compared to unprocessed (dry) common bean seeds, the thermal treatments (except cooking) and biological treatments (except 4 and 5-day germination) had no effect (P>0,05) on the concentrations of polyphenols in the seeds. The thermal treatments and solid-state fermentation had no effect (P>0,05) on the antioxidant activity (Radical Scavenging Activity – RSA%) of the seeds. The process of germination (4 and 5 days) led to significant (P<0,05) increased antioxidant activity in the seeds. For each separate treatment, both thermal and biological, positive correlation between content of polyphenols and RSA% of the seeds was observed. A red-seed common bean cultivar Małopolanka showed highest concentration of polyphenols as well as highest antioxidant activity in the seeds. It is concluded that the process of germination of Małopolanka seeds could be considered as a means of development a functional food product (with enhanced antioxidant potential).