A table saw includes a worktable, a left extension frame and a right extension frame respectively slidably mounted at left and right sides of the worktable, a scale unit including a first scale, a second scale and a third scale respectively mounted at the worktable, the left extension frame and the right extension frame, and an indicator unit including a first indicator, a second indicator and a third indicator respectively disposed to aim at the first, second and third scales. Thus, when operating the table saw to cut a workpiece, the user can selectively pull out the left or right extension frame and use the corresponding scale and indicator for quickly judging the correctness of the length to be cut.