A magnetic data processing device may include an encryption magnetic head structured to read the magnetic data recorded on the medium. The encryption magnetic head may include a magnetic data reading part structured to read the magnetic data of the medium to output an analog output signal; a demodulation electronic component structured to demodulate the analog output signal outputted from the magnetic data reading part to generate a digital demodulated signal; and an encryption electronic component structured to generate an encrypted signal obtained by encrypting the demodulated signal demodulated by the demodulation electronic component. The encryption electronic component may include at least a first buffer, a second buffer and a third buffer structured to store data having been read at an insertion time and an ejection time of the medium.