In semi-autonomous driving, it requires drivers to take over driving under necessary situations. To take over driving safely, it is important to avoid accidents caused by the decrement of arousal level. Therefore, mechanism to increase and maintain arousal level is needed. To achieve satisfying safe driving, the increment of arousal level should be in comfortable state. Many studies presented evaluations of arousal level, but there is no evaluation of comfortable arousal. In this study, we objectively evaluated both arousal and comfort using brainwave and heart rate variability (HRV), proposed to analyze time-series data, and compared various biological indexes with subjective evaluation by correlation analysis. The result shows significant correlations between objective and subjective evaluation results for both comfort and arousal indexes. Time series analysis of pNN50 as HRV index and β/α as brainwave index, which were significantly correlated with SAM results, shows the possibility of evaluating comfort and arousal with those indexes.