A tailstock includes a main body, a lathe center unit arranged in a hollow hole of the main body, a sliding base coupled with the main body and having a slider configured at a side thereof for pairing a slide rail, and a clamping unit configured in the sliding base. The clamping unit for increasing clamping force of the tailstock further includes a connection plate having at least one positioning hole to connect the main body, at least one hydraulic rod bridging the slider and the main body, a plurality of loading devices ring-set about the hydraulic rod, and a plurality of sleeves ring-set with the corresponding loading devices.