1. A video signal processing device which processes a three-dimensional (3D) video signal including a left-eye image and a right-eye image using a frame-sequential technique, said video signal processing device comprising: an on-screen display (OSD) control unit configured to generate a left-eye superimposition image and a right-eye superimposition image; a superimposing unit configured to superimpose the left-eye superimposition image on the left-eye image and the right-eye superimposition image on the right-eye image, so as to generate an output image; and a video output unit configured to provide the output image, wherein said OSD control unit includes: a first register which holds a left-eye parameter for generating the left-eye superimposition image; a second register which holds a right-eye parameter for generating the right-eye superimposition image; and an OSD processing unit configured to sequentially generate the left-eye superimposition image and the right-eye superimposition image, by switching between said first register and said second register, and wherein said OSD control unit is configured to generate the left-eye superimposition image and the right-eye superimposition image, by shifting positions of pixels in a predetermined image based on the left-eye parameter and the right-eye parameter.