Disclosed is a reagent for prothrombin time measurement, wherein the reagent contains a liposome composition containing a first liposome having a phospholipid layer, a second liposome having a phospholipid layer of a different composition from that of the first liposome, and tissue factor, wherein the tissue factor is associated with the phospholipid layer of at least one of the first liposome and the second liposome； the first liposome contains a phosphatidylcholine compound, a phosphatidylethanolamine compound, and a phosphatidylserine compound； and the second liposome contains at least one phospholipid selected from the group consisting of a phosphatidylcholine compound and a phosphatidylethanolamine compound.
