A grinder with granularity adjusting mechanism, comprising a container for holding condiments and a grinding head assembly connected to the container for grinding the condiments; the grinding head assembly comprises: a driving component mounted on top of the container, the driving component having an axis; a female grinding head rotatably mounted on the driving component, the female grinding head having a first through hole, the driving component passing through the first through hole, the first through hole defining an inner wall; a male grinding head placed inside the first through hole and engaged to the driving component and movable along the axis of the driving component, the male grinding head having a peripheral wall; a cover covering the grinding head assembly; the grinding head assembly further comprises an adjusting knob, with a connecting portion, engaged to the driving component, the connecting portion has a height, the inner wall of the first through hole and the peripheral wall of the male grinding head are provided with matching grinding teeth, the adjusting knob changes a gap between the male grinding head and the female grinding head by moving axially the male grinding head, the driving component, the male grinding head, the female grinding head are installed in a housing, the housing having a rotatable detachable cover the cover engages the connecting portion of the adjusting knob, characterized in that: the cover has a bottom surface and a protrusion on the bottom surface, the protrusion has a recess for receiving the connecting portion, the recess has a depth greater than the height of the connecting portion of the adjusting knob, the recess and the connecting portion having a matching profile, the driving component further comprises a connecting seat and a connecting rod mounted on the connecting seat, the male grinding head defining a second through hole adapted for the connecting rod passing through, the top end of the connecting rod is threaded for connecting to the adjusting knob, the top end of the connecting rod having a threaded periphery and the adjusting knob having a threaded hole for coupling with the connecting rod, and a spring is provided between the male grinding head and the connecting seat for pushing the male grinding head away from the connecting seat. a driving component mounted on top of the container, the driving component having an axis; a female grinding head rotatably mounted on the driving component, the female grinding head having a first through hole, the driving component passing through the first through hole, the first through hole defining an inner wall; a male grinding head placed inside the first through hole and engaged to the driving component and movable along the axis of the driving component, the male grinding head having a peripheral wall; a cover covering the grinding head assembly; the grinding head assembly further comprises an adjusting knob, with a connecting portion, engaged to the driving component, the connecting portion has a height, the inner wall of the first through hole and the peripheral wall of the male grinding head are provided with matching grinding teeth, the adjusting knob changes a gap between the male grinding head and the female grinding head by moving axially the male grinding head, the driving component, the male grinding head, the female grinding head are installed in a housing, the housing having a rotatable detachable cover the cover engages the connecting portion of the adjusting knob, characterized in that: the cover has a bottom surface and a protrusion on the bottom surface, the protrusion has a recess for receiving the connecting portion, the recess has a depth greater than the height of the connecting portion of the adjusting knob, the recess and the connecting portion having a matching profile, the driving component further comprises a connecting seat and a connecting rod mounted on the connecting seat, the male grinding head defining a second through hole adapted for the connecting rod passing through, the top end of the connecting rod is threaded for connecting to the adjusting knob, the top end of the connecting rod having a threaded periphery and the adjusting knob having a threaded hole for coupling with the connecting rod, and a spring is provided between the male grinding head and the connecting seat for pushing the male grinding head away from the connecting seat.