Recently, formaldehyde liberated from wallpapers, furnitures and adhesive agents in new buildings and houses cause troubles in human health, and this is called the sick building symdrome. In this study, the carbonaceous materials are prepared from coffee grounds by microwave treatment or by surface-treatments with two different silane coupling agents. We estimated the removal efficiency of formaldehyde by such materials. The water contents of coffee grounds are larger than those of other wastes and thus they were easily carbonized. Both the amount of formaldehyde adsorbed onto the carbonaceous materials and the adsorption rate increased with increasing microwave treatment period, and increased with increasing concentration of silane coupling agents, because the numbers of amino groups on the carbonaceous materials increase. The carbonaceous materials prepared from the coffee grounds would be utilized for adsorbates to remove formaldehyde.