Characteristics of tomato root for rootstocks were investigated by measuring average root diameter. The root diameter of the cultivar for rootstock became larger than that of scion cultivar at later growth stage. The root diameter was similar among the same line of rootstock cultivars and there was positive correlation between root diameter and tree vigor (R2=0.635). The information of root structure related root metabolism for high productivity will be more important in addition to disease and environmental stress resistance.