Disclosed is a method for preventing metal catalyst particles supported on a support and formed of a catalytically active metal or metal-containing alloy from coarsening, the method comprising: dispersing an anti-coarsening compound having a coarsening temperature higher than that of the metal catalyst, in at least one region selected from the group consisting of interstitial spaces among the metal catalyst particles and contact sites between the support and the metal catalyst particles. The electrode catalyst is structurally stable while not causing degradation of electrochemical quality, and thus can improve the longevity properties of a fuel cell.