The purpose of the invention of the present applicationis to provide a medical material and a blood purificationapparatus each having high anti-thrombotic properties and highsafety. The apparatus is produced by incorporating therein amedical material which has a hydrophilic copolymerizationpolymer present on a surface thereof which is to be in contactwith blood, wherein particulate protuberances each having aparticle diameter of 50 nm or more are present on the surfacewhich is to be in contact with blood at a density of 3particles/µm2 or less and the relaxation time of adsorbed waterin the hydrophilic copolymerization polymer is 2.5 × 10 -8 secondsor shorter and 5.0 × 10 -10 seconds or longer at -40°C.
