A method of separating activated human protein C, which comprises bringing a mixture containing activated human protein C having a gamma-carboxyglutamic acid (Gla) domain in the presence of a calcium ion into contact with a fixed antibody comprising an insoluble carrier and fixed thereto an antibody to a complex of human protein C and a calcium ion bound to the Gla domain whereby the activated human protein C is captured by the fixed antibody in the form in which the calcium ion is bound to the Gla domain. A method is also provided for separating activated human protein C from a mixture containing human protein C and activated human protein C, which comprises bringing a first mixture containing human protein C and activated human protein C having a Gla domain into contact with a first fixed antibody comprising an insoluble carrier and fixed thereto a first antibody to human protein C but not to activated human protein C to form a second mixture substantially free from human protein C while the human protein C is captured by the first fixed antibody, and bringing the second mixture in the presence of a calcium ion into contact with a second fixed antibody comprising an insoluble carrier and fixed thereto a second antibody to a complex of human protein C and a calcium ion bound at the Gla domain, whereby the activated human protein C is captured by the second fixed antibody in the form in which the calcium ion is bound to the Gla domain.