A camera device, comprising: an image sensor unit; and a measurement unit configured to divide image data acquired by the image sensor unit into a plurality of areas; measure a change in the mean value of the luminance signal in each of the areas for a predetermined time period and store (S802, S803) a longest time period during which a state where there is no change in the mean value of the luminance signal is maintained, and a minimum value and a maximum value of the mean value of the luminance signal for the predetermined time period after the predetermined time period has lapsed, wherein when the longest time period is equal to or less than a preset threshold, the measurement unit determines that the change constantly occurs (S804 YES) and specifies the corresponding area as a measurement area for determining that a video-image abnormality has occurred when there is no change in the mean value of the luminance signal in the measurement area, and when the longest time period is greater than the preset threshold (S804 NO), the measurement unit determines whether a ratio of the maximum value and the minimum value is equal to or smaller than a preset value, and if it is determined that the ratio is equal to or smaller than the preset value, the measurement unit determines that the change hardly occurs (S805 YES) and specifies the corresponding area as a measurement area for determining that a video-image abnormality has occurred when there is a change in the mean value of the luminance signal in the measurement area, and wherein the state where there is no change in the mean value of the luminance signal indicates that the change is less than 10% of a rating value. an image sensor unit; and a measurement unit configured to divide image data acquired by the image sensor unit into a plurality of areas; measure a change in the mean value of the luminance signal in each of the areas for a predetermined time period and store (S802, S803) a longest time period during which a state where there is no change in the mean value of the luminance signal is maintained, and a minimum value and a maximum value of the mean value of the luminance signal for the predetermined time period after the predetermined time period has lapsed, wherein when the longest time period is equal to or less than a preset threshold, the measurement unit determines that the change constantly occurs (S804 YES) and specifies the corresponding area as a measurement area for determining that a video-image abnormality has occurred when there is no change in the mean value of the luminance signal in the measurement area, and when the longest time period is greater than the preset threshold (S804 NO), the measurement unit determines whether a ratio of the maximum value and the minimum value is equal to or smaller than a preset value, and if it is determined that the ratio is equal to or smaller than the preset value, the measurement unit determines that the change hardly occurs (S805 YES) and specifies the corresponding area as a measurement area for determining that a video-image abnormality has occurred when there is a change in the mean value of the luminance signal in the measurement area, and wherein the state where there is no change in the mean value of the luminance signal indicates that the change is less than 10% of a rating value.