An endoscope apparatus 1 includes a transparent member 32 provided at a distal end of an insertion portion of an endoscope 2, opposed to an image pickup optical system, a transducer 37 attached to an inner surface of the transparent member 32, a diffraction grating 40 provided on an outer surface of the transparent member 32, for converting ultrasound vibration from the transducer 34 to a surface acoustic wave Φ that propagates on the outer surface of the transparent member 32 and a conversion section 32a provided in an outer peripheral corner of the transparent member 32 for converting the surface acoustic wave Φ to a bulk wave Φb that scatters into the transparent member 32.
