PURPOSE: To observe an optical image and an acoustic wave image at the same time all the time regardless of the position of a slide member by providing an optical observing means which has an optical head and an ultrasonic observing means which has an ultrasonic wave head.

CONSTITUTION: When optical images and ultrasonic wave images of individual samples installed on the stage 7 of a sample table 5 are observed at the same time, the two samples are provided at an interval equal to the interval between an ultrasonic wave head 15 and one of optical heads 17aW17d. Then, a goniometer 3 mounting the sample table 5 is arranged, for example, almost in the center of a movement range on an X-Y stage. Further, the slide member 54 is so moved that the head 15 and one of the heads 17aW17d face the samples to be observed on the stage 7 respectively. Consequently, the optical image and ultrasonic wave image are observed at the same time.