To address the issues of viewing safety in stereoscopic three-dimensional television, it is important to investigate determinants of visual discomfort in viewing stereoscopic images. In stereoscopic viewing, it is well known that visual discomfort can be induced by excessive binocular disparity, fast changes in binocular disparity, and binocular asymmetry. However, subjective sensation of visual discomfort could also be substantially different depending on other characteristics of visual stimulus given the complexity of the visual system. From previous studies that have investigated the relation between stimulus characteristics and binocular fusion limit, we speculate that stimulus width (i.e., object width in the stereoscopic scene) can also affect the perceived visual discomfort of stereoscopic images. This paper investigates the effect of stimulus width on visual discomfort by measuring subjective visual discomfort and binocular fusion time. Experimental results show that smaller stimulus width could induce more visual discomfort and increase binocular fusion time.