To provide a data recording device capable of suppressing a data recording amount while reliably recording fine variation of a waveform and easily detecting an abnormal variation part of the waveform after the recording.

In the data recording device converting an analog input signal to digital data by an A/D converter and storing it into a data memory, an extreme point detection part detecting an extreme point of the analog input signal on the basis of the digital data converted and output from the A/D converter is provided between the A/D converter and the data memory. The extreme point data in which a waveform data value of each detected extreme point and the number of sampling times between the extreme points are paired are stored in the data memory.