To provide an electric discharge drilling device capable of drilling fine holes in predetermined size without depending on complex detection and control techniques, and capable also of easily adjusting their size.

A bypass circuit 8 comprising a semiconductor switching element 7 is connected in parallel with a needle electrode 1 and a counter electrode 2. A light-emitting element 5 which emits light using a discharge current upon the application of a high voltage and a light-receiving element 20 which receives the light are used to detect the discharge current. When the output level of the light-receiving element 20 is equal to or greater than the threshold value of a comparator 23, the semiconductor switching element 7 is triggered by a trigger circuit 25 to cause the discharge current from the needle electrode 1 to flow from the bypass circuit 8 to ground to instantaneously shut off the discharge. Adjusting the threshold value of the comparator 23 using a threshold adjuster 22 varies the time required to actuate the trigger circuit 25, thereby making adjustable the size of holes drilled in film 3.