A method for determining nucleotide sequence encompasses: injecting a solution containing a sample DNA into a chip cartridge provided with a detecting electrode, to which a probe DNA is immobilized; introducing an intercalator solution in the chip cartridge; obtaining a current-voltage characteristic curve by measuring a current in the solution due to an electrochemical reaction of the intercalator through the detecting electrode; obtaining a baseline by linearly approximating the current-voltage characteristic curve; obtaining a net current value by subtracting, from a peak current value of the current-voltage characteristic curve, a baseline current value obtained from the baseline at a peak voltage value defining the peak current value; and identifying a nucleotide sequence in the sample DNA, using the net current value.