A worktable includes a first platform made of metal, a mounting structure fixed to the first platform and being utilized to mount the first platform on a machine, and at least one second platform made of granite and detachably joined to a lateral peripheral edge of the first platform and connected to the mounting structure in order to prevent the at least one second platform from disengagement from the first platform. Additionally, the first platform includes a first top side and the at least one second platform includes a second top side cooperating with the fist top side to form a flat surface, and with the flat surface adapted to allow a workpiece that is moved thereon to be manufactured precisely.