A method for fabricating metal nanoparticles, the method comprising: forming a solution comprising: water as the only solvent; a first metal salt which provides a first metal ion or an atomic group ion comprising the first metal ion in the solvent; a second metal salt which provides a second metal ion or an atomic group ion comprising the second metal ion in the solvent; a first surfactant which forms micelles in the solvent; and a second surfactant which forms micelles together with the first surfactant in the solvent; and forming the metal nanoparticles by adding a reducing agent to the solution, wherein the first metal ion or the atomic group ion comprising the first metal ion has a charge opposite to a charge at an outer end portion of the first surfactant, and the second metal ion or the atomic group ion comprising the second metal ion has a charge which is the same as the charge at the outer end portion of the first surfactant, the first metal ion or the atomic group ion comprising the first metal ion, and the second metal ion or the atomic group ion comprising the second metal ion form a shell portion of the metal nanoparticles in a micelle region which the first surfactant forms, a hollow core is formed inside of the metal nanoparticles, the cavity of the metal nanoparticles is formed in a micelle region which the second surfactant forms, the cavity is an empty space which is continuous from one region of the outer surface of the metal nanoparticles, a concentration of the first surfactant is 1 time to 5 times a critical micelle concentration to the solvent, the critical micelle concentration is the lower limit of the concentration at which the surfactant forms a micelle of molecules or ions in a solution, and a molar concentration of the second surfactant is 0.01 time to 1 time a molar concentration of the first surfactant. forming a solution comprising: water as the only solvent; a first metal salt which provides a first metal ion or an atomic group ion comprising the first metal ion in the solvent; a second metal salt which provides a second metal ion or an atomic group ion comprising the second metal ion in the solvent; a first surfactant which forms micelles in the solvent; and a second surfactant which forms micelles together with the first surfactant in the solvent; and forming the metal nanoparticles by adding a reducing agent to the solution, wherein the first metal ion or the atomic group ion comprising the first metal ion has a charge opposite to a charge at an outer end portion of the first surfactant, and the second metal ion or the atomic group ion comprising the second metal ion has a charge which is the same as the charge at the outer end portion of the first surfactant, the first metal ion or the atomic group ion comprising the first metal ion, and the second metal ion or the atomic group ion comprising the second metal ion form a shell portion of the metal nanoparticles in a micelle region which the first surfactant forms, a hollow core is formed inside of the metal nanoparticles, the cavity of the metal nanoparticles is formed in a micelle region which the second surfactant forms, the cavity is an empty space which is continuous from one region of the outer surface of the metal nanoparticles, a concentration of the first surfactant is 1 time to 5 times a critical micelle concentration to the solvent, the critical micelle concentration is the lower limit of the concentration at which the surfactant forms a micelle of molecules or ions in a solution, and a molar concentration of the second surfactant is 0.01 time to 1 time a molar concentration of the first surfactant.