Abstract: Proposed are a contrast agent containing an iodinated unsaturated fatty acid ethyl ester derived from vegetable oil, a non-iodinated unsaturated fatty acid ethyl ester, and sulfur dioxide (SO2), and a production method thereof. The contrast agent having a similar contrast effect is synthesized using vegetable oil as a substitute for poppy seed oil, which is unstable in terms of supply and is expensive. In addition, the long-term stability problem of an iodine-based contrast agent is solved by adding a non-iodinated unsaturated fatty acid ethyl ester and sulfur dioxide.