Ankle-brachial pressure index (ABI) measured using a conventional Doppler method is an independent predictor of the number of coronary vessels affected in coronary artery disease (CAD). Recently, a new clinical device has been developed to measure ABI using an oscillometric method. It is unclear whether ABI measured using this device is a significant predictor of the severity of coronary atherosclerosis. We retrospectively included 87 patients from our outpatient clinic who had ever undergone coronary angiography. ABI was determined in all subjects using the new ABI-form device. The lower value of ABI in either limb was used for analysis. We divided our subjects into two groups, with either ABI less than 0.9 or at least 0.9, and compared basal characteristics between groups. We analyzed the relationship between ABI and the severity of CAD. In addition, we calculated the sensitivity, specificity, and positive and negative predictive values of ABI less than 0.9 in predicting multivessel (two-vessel + three-vessel) involvement in our patients. There were 15 patients with ABI less than 0.9 and 72 with ABI at least 0.9. Patients with ABI less than 0.9 were older and had higher plasma levels of uric acid. The prevalence of diabetes mellitus, hypertension, smoking, and diuretic use was significantly higher in patients with ABI less than 0.9. In addition, the group with ABI less than 0.9 had a lower prevalence of one-vessel CAD and higher prevalence of three-vessel or multivessel CAD. The sensitivity, specificity, and positive and negative predictive values of ABI less than 0.9 in predicting multivessel CAD were 22%, 96%, 93%, and 34%, respectively. In conclusion, ABI measured using the automated oscillometric method can be used to predict the severity of coronary atherosclerosis in patients with CAD.