Abstract: Medical coagulation apparatus which reduces current that flows through the interior of a living body, and which does not produce thermal burning accidents caused by high-frequency current in an opposing electrode. Current generated by resonance on a secondary side L2 of a monostable multivibrator M flows into a primary side L1 from an amplifier 39. As a result, a high potential is generated on the secondary side L2 so that a unipolar discharge is produced by a needle electrode 16 connected to the secondary side. An arc discharge at the needle electrode 16 is guided by argon gas jetted from a nozzle 14 of a hand piece 10, irradiates tissue of a living body 50 and coagulates the tissue. The medical coagulation apparatus does not require an opposing electrode plate because the needle electrode 16 connected to the secondary side of the transformer produces the unipolar discharge.