The present invention relates to a fusion peptide wherein a self cell-penetrating Tat peptide having a self penetrating signal is bound to a human parathyroid hormone-derived peptide, a preparation thereof, and a skin slimming cosmetic composition comprising the same. Since the fusion peptide wherein the Tat peptide is bound to the human parathyroid hormone-derived peptide has high stability and superior skin absorption, the present invention provides a skin slimming agent having superior lipolysis effects and improved durability of the effects.