PURPOSE: To facilitate chucking and detaching of a work to be ground at a chucking equipment by a method wherein the work to be ground such as a crystal vibrator or the like is attracted to the chucking equipment by a pressure reducing means.

CONSTITUTION: A work 44 to be ground is pressed beforehand with a finger into an engaging groove 43a recessedly provided on a lower surface of a chucking equipment 43, then, under such a condition, a pressure in a cavity 42a of a cover body 42 is reduced by a pressure-recucing pump. Whereby, the work 44 to be ground is attracted by suction by small holes 43b, 43b bored on the chucking equipment 43. Subsequently, an arm 31 is oscillated and the work 44 is contacted with a spherical grinding surface 16a, thereafter, is pressed to the grinding surface 16a by a weight 51. Under this condition, motors 22, 53 are driven to oscillate a lap plate 16 while rotating, thus, a grinding work of the work 44 to be ground may be effected by the spherical grinding surface 16a of the lap plate 16.