The present invention relates to a method for manufacturing an electrode of a supercapacitor, comprising: (A) providing a carbon substrate and a phosphorus-containing precursor, and mixing the carbon substrate and the phosphorus-containing precursor at a ratio of 1:100 to 1000:1 by weight; (B) heating the mixture of the carbon substrate and the phosphorus-containing precursor to a temperature between 300° C. and 1100° C. to obtain a P-doped carbon substrate; and (C) forming an electrode of a supercapacitor by using the P-doped carbon substrate. The present invention also relates to a supercapacitor which comprises: a first electrode; a second electrode; and an electrolyte that is interposed between the first electrode and the second electrode, wherein at least one of the first electrode and the second electrode is prepared by the above-mentioned method.