Disclosed are a catalyst for dehydrogenating a paraffinic hydrocarbon and a method of preparing the same, wherein the catalyst is configured such that a sponge-type alumina support having 3D meso/macro pores is directly impregnated with an active metal, thus decreasing the diffusion resistance of a material, realizing structural stability, and maximizing the distribution of the active metal in the support, thereby significantly increasing olefin conversion and selectivity. In this catalyst, the sponge-type alumina support is directly impregnated with the active metal to thus form an active metal layer inside the support having 3D meso/macro pores that are interconnected to each other.