Methods of fabricating graphene using an alloy catalyst may include forming an alloy catalyst layer including nickel on a substrate and forming a graphene layer by supplying hydrocarbon gas onto the alloy catalyst layer. The alloy catalyst layer may include nickel and at least one selected from the group consisting of copper, platinum, iron and gold. When the graphene is fabricated, a catalyst metal that reduces solubility of carbon in Ni may be used together with Ni in the alloy catalyst layer. An amount of carbon that is dissolved may be adjusted and a uniform graphene monolayer may be fabricated.