To spread the use of catalysts for fuel cells, there is a demand to develop a catalyst that uses less Pt and has a high power generation efficiency. An electrode catalyst includes a support particle containing a metal oxide and a precious-metal alloy supported on the support particle. The support particle includes multiple branches, a hole between the branches, and a pore. The pore is surrounded by the branches and the hole. The precious-metal alloy includes a precious metal element and at least one or more transition elements.