PURPOSE: To improve the reliability of data by converting digital data into a prescribed waveform and recording the data in recording the FM digital data onto an audio tape to make the pulse width of the input and output waveform equal to each other.

CONSTITUTION: An output control circuit 1 checks digital data to be recorded stored in this circuit in advance according to the order of recording, selects which waveform stored in a storage device 2 is to be taken as an output for recording and gives the selection information to the storage device 2. The storage device 2 outputs the waveform information stored in advance to a DA converter 3 according to the selecting information. The DA converter 3 converts the said waveform information into a voltage signal and outputs it to a recorder 4. In reproducing the audio magnetic tape obtained in this way and waveform- shaping the reproduced waveform by a threshold value, the pulse width of the obtained rectangular wave train is almost equal to that of an input signal.