A physical unclonable function code generating method includes: providing a plurality of non-volatile memory cell pairs including a first non-volatile memory cell and a second non-volatile memory cell; comparing an initial state of the first non-volatile memory cell with an initial state of the second non-volatile memory cell, and generating a first physical unclonable function code according to a comparison result of the state; calculating a formation ratio difference of a logical level in the first physical unclonable function code; and adjusting the formation ratio difference by interactively performing forming operations on the first non-volatile memory cell and the second non-volatile memory cell when the formation ratio difference is greater than or equal to a ratio threshold.