crystal of whity part is slightly rotated against the crystal of black part and by adjusting the observation condition said part becomes black and the existing of dislocation can be confirmed in the meanwhile according to fig3 of the transmission electron microscope picture of ceramics product to be treated using conventional technique dislocation structure becomes a net work shape dislocated cell structure which is a stabilized arrangement by annealing treatment after plastic working in this figure dislocation is accumulated at the black net work part and consequently dislocation density becomes high and in whity part is the range where dislocation does not exist since dislocation does not exist at this whity part it does not change color to black even if the observation condition is changed thus the structure obtained by the method for surface toughening of the present invention is remarkably different from the structure obtained by conventional technique as the ceramics product to be processed a specimen of rectangular board shape silicon carbide sic 99 9 of 6 mm u00d7 6 mm u00d7 20 mm which is the product of ohmura taika co ltd is used plastic working shot blasting is carried out by jetting abrasives vertically to the surface of specimen from the thickness direction and measurements of dislocation density by tem observation and fracture toughness value are measured in table 6 conditions for plastic working shot blasting and results for quality characteristics of silicon carbide of before and after processing.