A porous particle has a controlled 3D network skeleton and communicating pores that include the voids of the skeleton and penetrate from the particle surface to the inside, a method produces the same, and a filler for chromatography uses the same. The porous particle mainly includes cellulose acetate or cellulose, is spherical, and has a 3D network skeleton and communicating pores that include the voids of the skeleton and penetrate from the particle surface to the inside. The retention time of dextran with a molecular weight of 2 million at a flow rate of 0.4 ml/min in a column with an inner diameter of 0.78 cm and a length of 30 cm filled with the porous particles is 20 minutes or more.