© 2018 IEEE. In recent years, Ministry of Health, Labor and Welfare reports that 25% of death causes in Japan are cardiovascular diseases such as heart disease and cerebrovascular disease etc. In order to measure the state of cardiovascular diseases, our group is working on the development of a compact blood flow velocity measuring device to measure blood flow dynamics. Currently, optimum probe position for measurement of carotid artery blood flow velocity is searched by use of the doppler signal. However, under some conditions such as the depth of the carotid artery, it may be difficult to judge whether blood flow velocity can be accurately measured with sound alone. The purpose of this study is to propose indices that can judge whether blood flow velocity waveform can be measured properly.