A dome-type camera comprising: a hemispherical dome cover; a lens unit; an aperture control unit for controlling an amount of aperture of an aperture mechanism of the lens unit; a zoom control unit which controls a zoom factor of the camera lens, and an illuminance measurement unit which measures an illuminance of light entering the camera lens, wherein, in case the lens unit has a non-zero offset from a spherical center of the dome cover towards the dome cover in a zenith direction of the dome cover, a first reference value for an amount of aperture is set in accordance with a tilt angle between the optical axis of the lens unit and the zenith direction of the dome cover, wherein the first reference value for an amount of aperture becomes smaller from an open value toward a closed value with the tilt angle changing from the zenith direction toward a horizontal direction of the dome cover being orthogonal to the zenith direction, a second reference value for an amount of aperture is set in accordance with an increase in the zoom factor, wherein the determirted second reference value for an amount of aperture is smaller from the open value toward the closed value with an increase in the zoom factor, and a third reference value for an amount of aperture is set in accordance with a decrease in the illuminance, wherein the third reference value for an amount of aperture becomes greater from the closed value toward the open value in accordance with a decrease in the illuminance, wherein the greater value after comparing the third reference value for an amount of aperture with the smaller of the first reference value for an amount of aperture and the second reference value for an amount of aperture in turn is used by the aperture control unit to control an aperture mechanism of the lens unit. a hemispherical dome cover; a lens unit; an aperture control unit for controlling an amount of aperture of an aperture mechanism of the lens unit; a zoom control unit which controls a zoom factor of the camera lens, and an illuminance measurement unit which measures an illuminance of light entering the camera lens, wherein, in case the lens unit has a non-zero offset from a spherical center of the dome cover towards the dome cover in a zenith direction of the dome cover, a first reference value for an amount of aperture is set in accordance with a tilt angle between the optical axis of the lens unit and the zenith direction of the dome cover, wherein the first reference value for an amount of aperture becomes smaller from an open value toward a closed value with the tilt angle changing from the zenith direction toward a horizontal direction of the dome cover being orthogonal to the zenith direction, a second reference value for an amount of aperture is set in accordance with an increase in the zoom factor, wherein the determirted second reference value for an amount of aperture is smaller from the open value toward the closed value with an increase in the zoom factor, and a third reference value for an amount of aperture is set in accordance with a decrease in the illuminance, wherein the third reference value for an amount of aperture becomes greater from the closed value toward the open value in accordance with a decrease in the illuminance, wherein the greater value after comparing the third reference value for an amount of aperture with the smaller of the first reference value for an amount of aperture and the second reference value for an amount of aperture in turn is used by the aperture control unit to control an aperture mechanism of the lens unit.