An optical device is to be disposed between a test screen and a test camera that captures an image on the test screen through the optical device. The optical device includes first, second, third and fourth lenses arranged from a camera side to a screen side in the given order. The first lens has a shape factor ranging from −10 to 5, the second lens is a positive lens and has a shape factor ranging from −15 to 2, the third lens is a positive lens and has a shape factor ranging from −30 to 1, and the fourth lens is a positive lens and has a shape factor ranging from −30 to 1. A ratio of a focal length of the optical device to that of the test camera ranges from 1 to 80.