A simple exercise test with vertical jumping was developed for children. The vertical acceleration wave form of back was measured with strain gauge type transducer. After amplification and rectification, the signal of positive acceleration was converted to frequency with voltage-to-frequency converter (VFC) and VFC signals were decoded by a digital counter. The digital output was normalized by gravitational value and defined as physical activity rate. 10 young males and 24 schoolchildren jumped at several frequencies and oxygen uptake, physical activity rate and heart rate were measured. Also 28 children under school age jumped arbitrary and heart rate and physical activity rate were recorded. The results showed that the oxygen uptake per body weight had good correlation to the physical activity rate (r=0.95) . Although heart rate was significantly different with ages, physical activity rate which was defined as an index of exrecise test, was no significant difference with ages and weights (α<0.05) . The results indicated that this jumping test was helpful to make exercise stress test for younger children.