A method of determining stiffness index of an arterial network is disclosed. The method comprises the steps of: obtaining a pulse waveform related to the arterial network estimating a source pulse based on at least one predetermined feature of the pulse waveform determining a plurality of characteristics of the pulse waveform based on a relationship between the pulse waveform and the source pulse and calculating the stiffness index of the arterial network based on the plurality of characteristics of the pulse waveform. An arterial stiffness index measuring device employing the above methodology is also disclosed therein.