We present the relationship between yield, mineral content, and the sap bleeding rate (SBR) caused by root pressure as an indicator of root activity in eight Dutch and eight Japanese tomato cultivars (including popular Japanese cultivar ‘Momotaro’) grown in a hydroponic system. Root dry weight in the rockwool slab was positively correlated with stem and leaf fresh weight. In the Dutch cultivars, the SBR remained high (over 20 mL・h^-1) as the root dry weight increased. In contrast, the SBR of Japanese ‘Momotaro’ series cultivars decreased. Ca in the tomato fruits and the SBR were higher in the Dutch cultivars than in the ‘Momotaro’ series. The SBR was found to positively correlate with fruit or total fresh weight. The higher SBR, which supports Ca transport to the fruits, probably led to the higher yields. The SBR might be a simplified indicator of selecting high-yielding cultivars in long-term cultivation.