PURPOSE: To make it possible to inspect bubbling phenomenon and discharging phenomenon synchronously and in real time in a record head wherein ink is heated to bubble for discharging the ink.

CONSTITUTION: There are provided two sets of measuring systems I and II respectively comprising objective lenses 9, 10 and TV cameras 11, 12 in positions facing each other in such a manner interposing a bubbling part and ink discharging part of a record head 100. An image signal processing circuit 30 is provided for reversing an image signal to be obtained from the camera 11 and for synthesizing the reversed image signal and an image signal to be obtained from the camera 12, so as to display the synthesized image on a monitor 21.