The present invention relates to a thiobenzimidazole derivative or a pharmaceutically acceptable salt thereof, and a composition for preventing or treating cancer, comprising the derivative as an active ingredient. The thiobenzimidazole derivative of the present invention exhibits cell toxicity by blocking the cell cycle of a cancer cell and inducing apoptosis when administered to an individual, as the derivative inhibits tubulin polymerization by being activated in the cancer cell, and, thus, the derivative can be used for prevention or treatment of cancer, desirably for prevention or treatment of triple-negative breast cancer.