PURPOSE: To relieve an operator of eye's fatigue and mental fatigue along with a higher measuring accuracy, by providing a TV camera, a cathode ray tube CRT, a coordinate detection means such as light pen and a computer in place of an magnifying mirror.

CONSTITUTION: A test piece 1 fractured is placed on a table 7 and the fracture 3 thereof is irradiated with a light source 8. The fracture 3 is taken with a TV camera 21 set above the test piece 1. In the photographing, a synchronous signal is fed to the TV camera 21 from a computer 22 to enable the monitoring X and Y coordinates on a screen of a CRT23. A video signal from the TV camera 21 is mixed with the synchronous signal to monitor and display the fracture 3 magnified on the CRT23. Thus, the fracture rates in brittleness and in the ductility S can be automatically determined simply by letting an operator surround the total area of the fracture 3 and the area of the fracture 4 in the brittleness on the screen of the CRT23 with a light pen 25.