An endoscope apparatus 2 according to the present invention includes an insertion portion 9 having a distal end portion 6 and at least two channels 54 and 63 an optical observation system 51 provided on one surface of the distal end portion so as to face an axial direction different from a direction of an insertion axis X of the insertion portion a first channel opening 41a provided on one surface of the distal end portion near the optical observation system an ultrasound transducer array 61 provided on the one surface of the distal end portion and having a scanning surface Z parallel to the insertion axis and a second channel opening 41b provided on a proximal end side of the ultrasound transducer array.
