A device for body fluid purification, comprising a container having an inlet and an outlet for a fluid and a means for preventing an adsorbent from flowing out of the container and an adsorbent charged in the container, the adsorbent comprising a spherical hydrogel, the spherical hydrogel having an average particle size in a range of from about 460 to 600 .mu.m and having a substantially uniform particle size and comprising an epoxidated cellulose having hexadecylamine immobilized thereon in an amount of 100 to 300 .mu.mol per gram of dry weight of said epoxidated cellulose, and water, wherein the weight ratio of said epoxidated cellulose having hexadecylamine immobilized thereon to the water is 2:8.