A method, suitable for an electronic apparatus with a first camera and a second camera, is disclosed for detecting whether the second camera is blocked accidentally. The method includes following steps. A first image is sensed by the first camera and a second image is sensed by the second camera simultaneously. A first brightness evaluation result is generated from the first image and a second brightness evaluation result is generated from the second image. Whether the second camera is blocked or not is determined according to a comparison between the first brightness evaluation result and the second brightness evaluation result.