Solid state spin trapping method was applied for measuring the scavenging activity of hydroxyl (OH) radical formed by the beta ray from tritiated water with four tea catechins, (−)-epicatechin (EC), (−)-epicatechin gallate (ECg), (−)-epigallocatechin (EGC) and (−)-epigallocatechin gallate (EGCg). The activity was in the order of EGCg > ECg > EGC > EC. This is consistent with the order of the number of phenolic hydroxyl groups in each catechin molecule. However, it was shown that EGCg had stronger activity than others, which suggested the interaction between the B ring and the gallate group.