To provide an endoscope apparatus where a surface acoustic wave can propagate in a direction mainly on a surface of an observation window, which can efficiently remove foul sticking to an observation window in a region of an observation field of view in the observation window.

The endoscope apparatus includes: a transparent member 32 provided at a distal end of an insertion portion of an endoscope, 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 37 to a surface acoustic wave Φ that propagates 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.