The invention discloses a countersink wrong and missed counting-prevention alarm device and alarm method for a bench drill. The alarm device comprises a bench drill main body and a counting alarm device which includes a data acquisition unit, a data processor, a central processing unit, a device controller and an alarm device; the data acquisition unit is used for outputting first signals after countersinking operation is performed once; the data processor decreases progressively the initial value of the preset number of the times of countersinking by 1 each time according to the first signals, and outputting second signals when the number of the times of countersinking is decreased to 0; the central processing unit outputs third signals according to the second signals; and the device controller controls the alarm device to be started according to the third signals. With the alarm device and alarm method of the invention adopted, the work defects of insufficient countersinking, missedcountersinking or redundant countersinking during countersinking operation can be avoided.