To provide an ion adsorbing resin which can adsorb and remove ions in ultrapure water and shows little elution of fine particles, ions and TOC (total organic carbon), and a porous ion adsorbing material.

The ion adsorbing resin is prepared by introducing ion exchange groups into the surfaces of polymer resin particles having ≤300 μm particle size and has 0.3 to 10 meq/g ion exchange capacity. The ion adsorbing porous material contains the ion adsorbing resin by 10 to 70 wt.% in the porous resin matrix including at least one thermoplastic resin particle having ≤300 μm particle size.