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