The present invention relates to a Krueppel-like factor 10 (KLF10) gene expression inhibitor promoting cartilage differentiation, and more specifically, to: a composition for promoting chondrocyte differentiation or treating cartilage diseases, containing a KLF10 gene expression inhibitor promoting cartilage differentiation and inhibiting the hypertrophy and dedifferentiation of chondrocytes; a cell therapeutic agent containing the composition; a method for promoting cartilage differentiation in bone marrow stem cells, comprising a step of expressing the composition in bone marrow stem cells; and a method for screening a chondrocyte differentiation promoter or a chondrocyte therapeutic agent. The present invention first examined the generation inhibition mechanism of indian hedgehog (IHH) protein of which the molecular biological mechanism has not yet been clearly examined, and ascertained that chondrocyte differentiation is promoted and chondrocyte hypertrophy is inhibited when chondrocyte differentiation is induced by expressing the KLF10 expression inhibitor in bone marrow stem cells. Therefore, the present invention has an advantage of enabling the use of bone marrow stem cells, which express a KLF10 expression inhibitor, as a chondrocyte therapeutic agent.