Abstract: An angle-adjustable workpiece seat includes a base having a bottom surface, a top surface having a concave primary supporting surface, a confining surface, a receiving groove and holes, a locking piece having a pressing surface and corresponding holes, threaded elements threaded through corresponding holes of the base and the locking piece for driving the locking piece to laterally translate in the receiving groove, and a sliding member having a top V-shaped positioning surface and a bottom sliding rail complementary to a sliding groove formed by said pressing, primary supporting and confining surfaces and having a primary sliding surface matching against and slidable on the primary supporting surface. The bottom surface can detachably attach thereunder two identical cylinders. The positioning surface can include two plane surfaces each of which detachably attaches thereto a pad piece.