1. A display apparatus with an image-capturing function, comprising: an outputting unit configured to output an image signal to an external apparatus; an inputting unit configured to input an image signal from the external apparatus; an image-capturing unit; a display unit; a corrector configured to perform image-capture-distortion correction and display-distortion correction on an image signal captured by the image-capturing unit; a controller configured to control the corrector to perform the image capture-distortion correction if a correction mode of the image capture-distortion is set, control the corrector to perform the display distortion correction if a correction mode of the display distortion is set, and perform the image capture-distortion correction and the display distortion correction at the same time if a correction mode of the image capture-distortion and the correction mode of the display-distortion are set; an image combining unit configured to combine an external input image input from the inputting unit with an image captured using the image-capturing unit; and a setting unit configured to set a type of distortion correction performed by the corrector and to determine whether or not the image combining unit is to perform image combining, wherein the controller performs the control according to the settings made by the setting unit, wherein the corrector performs the image-capture-distortion correction using a first correction table that contains image-capture-distortion correction data and performs the display-distortion correction using a second correction table that contains display-distortion correction data by a single circuit in a time-sharing processing, wherein when the image combining unit performs image combining to generate a combined image, the corrector performs image-capture inverse distortion correction on the external input image by applying distortion equal to image-capture distortion caused by the image-capturing unit, and the corrector performs image-capture-distortion correction and display-distortion correction on the combined image.