A porous cellulose aggregate characterized by having a secondary aggregate structure resulting from aggregation of primary cellulose particles, having a pore volume within a particle of 0.265 to 2.625 cm.sup.3/g, containing I-type crystals and having an average particle size of over 30 to 250 .mu.m, a specific surface area of 0.1 to less than 20 m.sup.2/g, a repose angle of 25.degree. to less than 44.degree. and a swelling degree of 5% or more, and characterized by having the property of disintegrating in water.