PURPOSE: To simultaneously measure plural separated and developed arrays by detecting the radiations irradiated from a radioactive labeling material while one-dimensionally separating and developing the same on a supporting medium and obtaining the positional information on the radioactive labeling material in the form of figures, symbols, etc.

CONSTITUTION: Both ends of the gel supporting medium 1 for electrophoresis are respectively immersed into an upper buffer soln. tank S1 and a lower buffer soln. tank S2 which are connected by a power source V for electrophoresis. The power source V is controlled by the set value (a) outputted from a signal processing circuit 3. The samples provided with the radioactive labeling are respectively injected into the plural slots provided in the upper part of the medium 1, then the sample starts migrating toward the bottom end at the speed corresponding to the potential difference between the tanks S1 and S2. A long-sized radiation measuring instrument 2 is disposed on the surface of the medium 1. The electric signal outputted from the instrument 2 is the signal for each migration array and is inputted in real time into a signal processing circuit 3 where the signal is subjected to signal processing such as correction of data. Four kinds of signals are obtainable with, for example, base specific DNA fragments.