A thiazoline derivative represented by Formula (I): ##STR00001## wherein R is a cyclic hydrocarbon group which may be substituted, or a heterocyclic group which may be substituted; X is a bond or a divalent chain hydrocarbon group which may be substituted; X' is a bond or --N(R.sup.5)--; Y is a divalent hydrocarbon group which may be substituted; Y' is a bond or --C(.dbd.O)--; ring A is a nitrogen-containing heterocycle which may be substituted; Z.sup.1 and Z.sup.3 are each independently a bond or a divalent chain hydrocarbon group which may be substituted; Z.sup.2 is a bond or --N(R.sup.6)--; and B is a group represented by the formula: ##STR00002## which is useful as a therapeutic drug for thrombosis, is provided.