a method for improving the toughness of the surface of a ceramics product , characterized in that the ceramics product is substituted to a plastic working wherein a dislocated structure is formed in the sub - surface regions thereof , the structure being in a straight line form and covering uniformly over the whole of the ceramics product and having a dislocation density of 1 × 10 4 to 9 × 10 13 cm − 2 , by the use of a jet material comprising fine particles having a convexly curved surface and having an average particle size of 0 . 1 μm to 250 μm and a vickers hardness of 500 or more and of a hardness of the ceramics products + 50 or less ; and ceramics products which have a dislocated structure being in a straight line form and covering uniformly over the whole of the surface thereof and having a dislocation density of 1 × 10 4 to 9 × 10 13 cm − 2 .