To automatically recover the base line when the base line of an electrocardiogram waveform substantially fluctuates by the body movement of a testee body or the like as to the electrocardiogram waveform detection and display device for the medical image diagnostic device.

This device is provided with an automatic electrocardiogram waveform base line control part 9 for fetching electrocardiograph signals from a post stage part from a body movement noise filter 3, comparing it with a prescribed threshold value, and when the electrocardiogram waveform exceeds it and a base line position fluctuates, generating base line recovery signals and discharging a capacitor inside the body movement noise filter 3. Thus, when the base line of the electrocardiogram waveform substantially fluctuates by the body movement of the testee body or the like, the base line is automatically recovered to a zero level.