The present invention provides not only a medical material having high antithrombotic characteristics and safety, but also a blood purification apparatus. The present invention is obtained by medical material being installed. The medical material wherein hydrophilic copolymers exit on surface contacting with blood, particulate projections having diameter more than 50 nm exit on the blood-contacting surface less than 3 pieces/ &mgr； m2, the hydrophilic copolymers' relaxation time of adsorbed water at 40 DEG C is less than 2.5x10<；SP>；-8<；/SP>；sec and more than 5.0x10<；SP>；-10<；/SP>；sec.
