The incorporation of deoxynucleoside triphosphates (dNTPs) catalyzed by polymerases is conventionally examined using gel electrophoresis autoradiography. Here, we studied an alternative method, pyrosequencing, to verify the incorporation of dNTPs containing unnatural nucleotides by polymerases. We found that the pyrosequencing method more rapidly and easily confirmed the incorporation of dNTPs than the conventional method, especially in the presence of low-efficiency dNTP polymerases. Furthermore, the method can detect the pyrophosphorolysis reaction just before the position of the unnatural nucleic acid, and the efficiency of incorporation just after it.