A flat-clinch stapler comprising: a base (10,10A) having a front end; a rear end opposite to the front end; and a middle segment located between the front end and the rear end; a magazine assembly having a rear end pivotally connected with the rear end of the base (10,10A); a handle device mounted above the magazine assembly and having a rear end pivotally connected with the rear end of the base (10,10A); a flat-clinch device having a slider capable of being driven by the handle device, slidably mounted on the middle segment of the base (10,10A), and having a through hole formed through the slider; a moving board mounted above the slider and having a bottom surface; and a rear end pivotally connected with the base (10,10A), wherein the moving board is restricted by the slider and prevented from descending before the slider is moved backwardly toward the rear end of the base (10,10A); characterised in that the slider has a front end adjacent to the front end of the base (10,10A); a clinch unit is mounted in the front end of the moving board; and the slider has a buffering device having a protrusion (51,51A) securely disposed on the bottom surface of the moving board, mounted through the through hole of the slider, and having a protrusion abutting section (511,511A); a block (52,52A) mounted on the middle segment of the base (10,10A), being slidable between the front end and the rear end of the base (10,10A), capable of being driven by the protrusion (51,51A) when the moving board is pivoted, and having a block abutting section (521,521A) abutted by the protrusion abutting section (511,511A), wherein at least one of the protrusion abutting section (511,511A) and the block abutting section (521,521A) is an inclined surface; and an elastic member (53,53A) extending toward the front end and the rear end of the base (10,10A) and abutting the block (52,52A) and the base (10,10A), wherein the base (10, 10A) has a guiding groove formed in the middle segment of the base (10, 10A) and extending toward the front end and the rear end of the base (10, 10A); the block (52,52A) is mounted on the guiding groove and capable of sliding along the guiding groove; and the block (52,52A) further has a rear side; a guiding section mounted in the guiding groove; a restricting section being a plate, located below and securely disposed on the guiding section, and having a width larger than that of the guiding groove; and a lump section located at the rear side of the block (52,52A). a base (10,10A) having a front end; a rear end opposite to the front end; and a middle segment located between the front end and the rear end; a magazine assembly having a rear end pivotally connected with the rear end of the base (10,10A); a handle device mounted above the magazine assembly and having a rear end pivotally connected with the rear end of the base (10,10A); a flat-clinch device having a slider capable of being driven by the handle device, slidably mounted on the middle segment of the base (10,10A), and having a through hole formed through the slider; a moving board mounted above the slider and having a bottom surface; and a rear end pivotally connected with the base (10,10A), wherein the moving board is restricted by the slider and prevented from descending before the slider is moved backwardly toward the rear end of the base (10,10A); characterised in that the slider has a front end adjacent to the front end of the base (10,10A); a clinch unit is mounted in the front end of the moving board; and the slider has a buffering device having a protrusion (51,51A) securely disposed on the bottom surface of the moving board, mounted through the through hole of the slider, and having a protrusion abutting section (511,511A); a block (52,52A) mounted on the middle segment of the base (10,10A), being slidable between the front end and the rear end of the base (10,10A), capable of being driven by the protrusion (51,51A) when the moving board is pivoted, and having a block abutting section (521,521A) abutted by the protrusion abutting section (511,511A), wherein at least one of the protrusion abutting section (511,511A) and the block abutting section (521,521A) is an inclined surface; and an elastic member (53,53A) extending toward the front end and the rear end of the base (10,10A) and abutting the block (52,52A) and the base (10,10A), wherein the base (10, 10A) has a guiding groove formed in the middle segment of the base (10, 10A) and extending toward the front end and the rear end of the base (10, 10A); the block (52,52A) is mounted on the guiding groove and capable of sliding along the guiding groove; and the block (52,52A) further has a rear side; a guiding section mounted in the guiding groove; a restricting section being a plate, located below and securely disposed on the guiding section, and having a width larger than that of the guiding groove; and a lump section located at the rear side of the block (52,52A).