The effect of steam and hydrogen treatments on the catalytic properties of a high-cell-density pure Ni honeycomb catalyst for methane steam reforming was investigated. A pretreatment consisting of steam treatment and subsequent hydrogen reduction at 1173 K significantly enhanced the catalytic activity of the Ni honeycomb catalyst at low temperatures below 1073 K. In situ X-ray absorption fine structure spectroscopy analysis showed that during the steam treatment, the surface Ni atoms were oxidized, and then these oxides were completely reduced to metallic Ni during the subsequent hydrogen reduction. The evolution analysis in surface morphology during pretreatment showed that many fine Ni particles formed on the surface. This surface structure was considered to be catalytically active for the methane steam reforming which is known to be structure sensitive.