An image signal storing unit stores an image signal provided from the outside. An image processing unit appropriately processes the image signal stored in the image signal storing unit in accordance with the instruction from an adjusting unit. A projecting unit projects, onto a display area, light corresponding to an image created by the image processing unit. A display size determination unit computes the display size of the picture plane displayed on a screen based on an image captured by the camera provided adjacent to the projection-type video-image display device. The display size determination unit then determines whether or not the display size of the picture plane is equal to or larger than a predetermined upper-limit size.