Hydrotreatment catalysts (Co-Mo/Al2O3, Ni-Mo/Al2O3 and Ni-W/Al2O3) were prepared by an impregnation method using an aqueous solution containing a chelating agent (nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) or trans-1,2-cyclohexanediamine-N,N,N＇,N＇-tetraacetic acid (CyDTA)). Co-Mo/Al2O3 and Ni-W/Al2O3 prepared with the chelating agents showed higher hydrodesulfurization (HDS) activity as well as hydrogenation (HYD) activity under high pressure (5.1 MPa) than those prepared without the chelating agents. Co-Mo/Al2O3 prepared with CyDTA showed ca. 70% higher HDS activity for benzothiophene (BT) than that prepared without it. HYD activity of Ni-W/Al2O3 for o-xylene was promoted about 65% by the addition of CyDTA. FT-IR of nitric oxide (NO) adsorbed on the sulfided Co-Mo/Al2O3＇s suggested that Co was highly dispersed over the catalyst surface when the catalysts were prepared with the chelating agents.