A sinker electric discharge machining apparatus for machining a workpiece by generating electric discharge in a work gap by applying a voltage having an OFF time, may include a discriminator for generating a first signal representing an abnormal state of the work gap, and a second signal representing a normal state of the work gap; and a pulse controller, in which a first extension factor and a second extension factor that is smaller than the first extension factor are set and a first reduction factor and a second reduction factor that is smaller than the first reduction factor are set. The pulse controller extends the OFF time using either the first or the second extension factor if the first signal is received. The pulse controller reduces the OFF time using either the first or the second reduction factor if the second signal is received.