The present invention relates to an image sensor unit including an image sensor that generates an image signal and a filter, and to an image taking apparatus that receives light from a subject and generates an image signal. The image sensor unit and the image taking apparatus achieve excellent photographing through day and night. They are provided with a filter including a transparent layer that is transparent to light in a visible light region regardless of the state of an electric field and is transparent to light in a predetermined variable transparent region containing an infrared light region and/or an ultraviolet light region in response to the state of the electric field, and electrodes that generate the electric field in the transparent layer on the application of a voltage.