A plasma or serum separator (10) for isolating plasma or serum from whole blood, comprises: a blood separation member (12), configured for separating blood applied to a first portion such that the plasma or serum of the blood is located in a second portion； a holding member (14) covering and holding the blood separation member (12)； a blood introducing portion (16) formed in a portion of the holding member (14) covering the first portion； a plasma or serum sampling aperture (18) formed in a portion of the holding member (14) covering the second portion； and at least one plasma or serum collecting cavity (22) arranged at the second portion in fluid communication with the plasma or serum sampling aperture (18) for collecting plasma or serum leaving the blood separation member (12) through the plasma or serum sampling aperture (18).
