Abstract: A signal processing method in autoradiography for determining base sequence of DNA or DNA fragment, employing groups of base-specific synthetic products which are complementary to the DNA or DNA fragment and a labeled with a radioactive element, said groups being resolved one-dimensionally in parallel relation to each other to form resolved rows on a support medium,which comprises a process including:(1) determining on each of the resolved rows a scanning line for signal processing;(2) detecting on each of the resolved rows sampling points on said scanning line; and(3) comparing and identifying the positions of said sampling points on the scanning lines among the resolved rows to obtain locational information on guanine, ademine, thymine and cytosine;said process being applied to digital signals corresponding to an autoradiograph having the locational information on the radioactively labeled synthetic products, said digital signals being obtained by the use of a stimulable phosphor sheet or by the use of a ra