In order to improve the time-consuming and inconvenient operation of measuring arterial elasticity, an arterial elasticity measurement for diabetic patients is developed that uses the elastic constant based on photoplethysmography (PPG)．As the artery vibrates in a radial direction, the elastic constant used for evaluating peripheral arterial elasticity can be derived based on the arterial pressure wave equation and the spring constant model. In addition, the relationship between the elastic constant and the brachial-ankle pulse wave velocity (baPWV) is investigated. The results of the statistical analysis indicate a significantly high correlation between the elastic constants computed by PPG and the radial pulse (p<0.001, correlation coefficient=0.85). The results also indicate a significant negative correlation between the baPWV and the elastic constant based on PPG (p<0.001, correlation coefficient =-0.701). Multivariate regression analysis also indicates a close relationship between them. In addition, the Student′s t test is used to examine the difference of the elastic constant computed by PPG between the experimental and control groups. A p-value less than 0.05 indicates that the difference between the two groups is statistically significant. These results suggest that the elastic constant based on PPG can effectively identify the characteristics of arterial elasticity between the experimental group and the control group, and that arterial elasticity can be measured quickly and effectively.