Deep root system may be a desirable plant character in upland rice due to greater water extraction capacity during intermittent drought. The objective was to assess deep root development of rice cultivars in relation to soil water extraction under moderate water-limiting upland conditions in a simple lysimeter experiment. In the lysimeter with 70 cm soil layer, time-domain reflectometers (TDR) were installed at 5, 15, 25, 45 and 65 cm depth to monitor soil water extraction at each depth, and minirhizotron method was applied to observe in situ root growth. An upland cultivar (Yumeno-hatamochi [YHM]) and a lowland cultivar (Nipponbare [NPB]) were used and two timings of drought were imposed during late vegetative stage (71-104 days after sowing [DAS] and 88-104 DAS). Volumetric soil water content in the surface layer (0-10 cm) decreased 35-39 % compared with 45 % in the well-watered plot at 104 DAS. Though differences in maximum rooting depth between the two cultivars were not detected by minirhizotron at any measurement occasion, YHM proliferated more roots below 20 cm from earlier growth stage with lower top-to-root ratio and higher deep root length ratio (proportion of root length below 30 cm depth), which had longer deep root length at 95 DAS compared with NPB. The proportion of soil water extraction from 45-70 cm depth to the total increased over 50 % as the drought progressed and YHM extracted more water from 45-70 cm depth than NPB. This study suggested that the number of adventitious roots penetrate into the deeper soil layer and proliferation of deep roots would be important for deep root development in rice. The advantage of deep root development should be more expected under severer water-limiting upland fields, where the gradient of soil water from shallow to deep layer was larger than the lysimeters of this study.