A separation column for ion chromatograph, which is packed with an organic porous ion exchanger having a three-dimensionally network structure which has a continuous pore structure comprising macropores connected with each other and, being present in the wall between them, a mesopore having a radius of 0.01 to 50 .mu.m, has a total pore volume of 1 to 50 ml/g, exhibits a value obtained by dividing the half width of the main peak of the pore distribution curve thereof by the radius of the peak top of the main peak of 0.5 or less, and has ion exchange groups introduced so that the exchanger has an ion-exchange capacity of 0.1 to 5000 .mu.g equivalent/g-dry organic porous ion exchanger. The separation column exhibits high performance capability especially for the separation and concentration of low molecular weight ions, and thus can be used for passing a sample solution through it with a reduced pressure while retaining a high capability for ion resolution.