For efficient methanol synthesis by CO 2 hydrogenation, catalysts prepared by mixing sponge copper and amorphous ZrO 2 were investigated. The commercial sponge copper itself exhibited catalytic activity for methanol synthesis by CO 2 hydrogenation. The sponge copper mixed with amorphous ZrO 2 in a mortar showed higher catalytic activity. Moreover, both CO 2 conversion and methanol selectivity were enhanced by wet milling using a planetary ball mill. Taking into consideration the structure, we found a mechanochemical interaction between the sponge copper and amorphous ZrO 2 by wet milling. These results showed that the strong interaction between the sponge copper and amorphous ZrO 2 caused by the mechanochemical treatment creates effective sites for methanol synthesis by CO 2 hydrogenation.