Visual fatigue is a common problem when viewing stereoscopic images. We propose a depth adjustment method that controls the amount of disparity in stereoscopic images using visual fatigue prediction and conducted subjective preference evaluation based on individual fusional response characteristics. Visual fatigue level is predicted by examining the characteristics of horizontal disparity. Viewers are classified into two groups (those with normal susceptibility to visual fatigue and those with high susceptibility to visual fatigue) according to individual fusional limit and speed of fusion, which are determined using a random dot stereogram test. Subjective preferences for the amount of depth adjustment are investigated based on the degree of fusion ability. Our experimental results support the suitability of the proposed depth adjustment method for reducing visual fatigue.