The method of manufacturing a graphene device includes forming an insulating material layer on a substrate, forming first and second metal pads on the insulating material layer spaced apart from each other, forming a graphene layer having a portion defined as an active area between the first and second metal pads on the insulating material layer, forming third and fourth metal pads on the graphene layer spaced apart from each other with the active area therebetween, the third and fourth metal pads extending above the first metal pad and the second metal pad, respectively, forming a first protection layer to cover all the first and second metal pads, the graphene layer, and the third and fourth metal pads, and etching an entire surface of the first protection layer until only a residual layer made of a material for forming the first protection layer remains on the active area.