A liposome containing a hydrophobic iodine compound represented by the following general formula (I) as a membrane component:

R¹—CO₂—R²

wherein R¹ represents a substituted or unsubstituted 2,3,5-triiodophenyl group or a substituted or unsubstituted 3,4,5-triiodophenyl group; and R² represents a hydrocarbon group having 10 or more carbon atoms, and an X-ray contrast medium, which comprises said liposome which is used for radiography of a vascular disease.