At a front end of the lateral arm of a surgical microscope apparatus, the apparatus has an intake port. A band is tied around the front end of the lateral arm so that a drape is drawn only to a surgical microscope. Drawing the drape to the surgical microscope results in clearing the field of vision of a surgeon. Part of the drape around the lateral arm and a longitudinal arm is not drawn, to cause no hindrance in operability of the surgical microscope. The lateral arm and the like are hollow to form an inner ventilating path without separately preparing ventilating tubes or the like for ventilation.