To obtain an image in which only groove can be seen floating up in a good contrast state and to make even a small groove formed on the surface on the image confirmable by irradiating a body to be inspected with light in a direction vertical to the extending direction of the groove on the surface of the body to be inspected.

The irradiating direction with an illuminator 15 is controlled by an illuminating direction controller 14 based on a signal showing the direction of diffracted light outputted from an optical sensor 13 so that a hard disk 12 may be illuminated in a direction vertical to the extending direction of the groove 12a on the surface of the hard disk 12. The hard disk 12 is illuminated in a direction vertical to the extending direction of the groove 12 on the surface of the hard disk 12, then, the light scattering from the groove 12a on the surface is intensely made incident into a lens barrel 16, besides, light reflected by parts other than the groove 12a has a strong regular reflection component, so that the only weak light is made incident into the lens barrel 16. Thus, the image with high contrast between the groove 12a and the parts other than the groove 12a is taken in by a CCD line sensor 17.