The invention provides a code generating apparatus and an OTP memory block. The code generating apparatus of present disclosure includes a plurality of first one time programming (OTP) memory cells, a reference signal provider and a sense amplifier. The first OTP memory cells are coupled to a first bit line. The reference signal provider provides a reference signal. Wherein, at least one of the first OTP memory cells provides a read current to the first bit line, and the sense amplifier compares the read current and the reference signal to generate an output code. A current value of the reference signal is set within a range, and the range is set by the bit current corresponding to a maximum bit count, such as that the output code is determined by a manufacturing variation of the at least one first OTP memory cell.