PURPOSE: To provide a device for measuring the wall movement of the whole periphery of the heart by means of an M mode methed and to provide a device for measuring the wall movement of the whole periphery of the heart from a tomographic image signal recorded on a recording medium such as an already photographed video tape or the like by means of an M mode method.

CONSTITUTION: A test data processor comprises an A/D converter 2 for digitizing a tomographic image signal of a subject obtained by a tomographic device 1, an image signal data memory 3 for recording image signal data, a means 4 for extracting image signal data on an arbitrary cursor line of the section of the subject from image signal data and outputting M mode image signal data, a D/A converter 5 for converting the M mode image signal data to analog, and an output device 6 for receiving the M mode image signal and displaying the M mode image of the subject. A signal output from a recording medium such as a video tape or the like can be also used as a tomographic image signal of the sabject.