Abstract: Provided are an electrocatalyst for a fuel cell having a large amount of catalyst metal particles supported on a carbon support and maintaining a high-dispersity state and a method of preparing the same. The electrocatalyst is characterized by being composed of catalyst metal particles having a secondary structure composed of at least one kind of primary metal particles having a particle diameter of 0.1 to 1.5 nm, or the catalyst metal particles having a core-shell structure of which the core is composed of metal particles having a particle diameter of 2.0 nm or less, and carbon particles. The method of preparing the electrocatalyst, including a first loading step for producing the core of catalyst metal particles wherein distances between the particles are controlled to 2.0 nm or less on a support and a second loading step for growing the catalyst metal particles, enables the amount of metal loaded on the support to increase without causing aggregation of the catalyst metal particles in the end.