An organic porous material having selective adsorption ability for boron, characterized in that it has an open cell structure comprising macro pores jointed to one another and, formed within the wall of the macro pore, meso pores having a pore diameter of 0.02 to 200 .mu.m, has a total pore volume of 1 to 50 ml/g, and contains a compound capable of forming a complex with boric acid introduced through a covalent bonding in an amount of 1 .mu.mol/g-dry porous material or more. The organic porous material exhibits improved ability for adsorbing boron and also is excellent in stability, and a boron removing module and an ultra-pure water production apparatus using the porous material have extremely high utility.