PurposeUltrasonography-derived carotid artery intima–media thickness (IMT) has been established as an early atherosclerotic imaging biomarker. The IMT reference value of a healthy person is approximately 0.1 × (every 10 years of age) + 0.2 (mm); accordingly, it requires an accuracy of at least 0.1 mm. However, one concern of IMT measurement is intervendor variability. In this study, we aimed to verify the intervendor variability using an IMT phantom.MethodsAn improved IMT phantom was developed, and it was possible to analyze the IMT by software for all vendors.ResultsWith the vendor-specific software, the maximum difference between the devices was 0.08 mm, and the difference in quartile range was 0.06 mm. On the other hand, with the vendor-independent offline software, the maximum difference between the devices was 0.16 mm, and the quartile range of variation was 0.06 mm.ConclusionThe intervendor variability assessed using our IMT phantom was less than 0.10 mm, and the on-board vendor-specific software was shown to reduce the difference between the devices significantly compared with the vendor-independent offline software. To further improve the vender difference, adjustment by means of vendor-specific software based on a standardized IMT phantom is warranted.