The present invention provides an image pick-up window defogging function-equipped built-in camera hand piece having a function of treating an affected area and an image observation function of observing the affected area or the like with a camera and capable of defogging the outer surface of an image pick-up window by preventing adhesion of cutting waste and water droplets to the image pick-up window. An image pick-up window defogging function-equipped built-in camera hand piece 1 of the present invention is provided with a defogging air flow path mechanism 4 in a surrounding position of an image pick-up window 15 arranged facing a cutting site of a cutting tool 16, wherein the defogging air flow path mechanism 4 branches from the air flow path system 91 and injects an air flow within a region from the outer surface of the image pick-up window 15 to the cutting site of the cutting tool 16 to shield an area between the outer surface of the image pick-up window 15 and the cutting site by the air flow to defog the outer surface of the image pick-up window 15.
