a cylindrical head main body which has an inlet through which air enters;

a plurality of slots which are formed in the head main body in a longitudinal direction thereof and distributed in a circumferential direction of the head main body; and

an internal insert which is inserted into the head main body and configured to guide air entering through the inlet toward the slots so that the air is discharged through the slots and flows along a surface of the head main body,

wherein the internal insert includes:

a plurality of guide plates which are disposed in the circumferential direction; and

a frame part which is configured to support the plurality of guide plates so that air blowing holes are formed between the plurality of guide plates, and

wherein each guide plate is configured to form:

a primary air blowing space which is formed between the guide plate and an arbitrary first plate part among a plurality of plate parts and which allows air entering through the air blowing holes to blow and be discharged through the slots; and

a secondary air blowing space which is formed between the guide plate and a second plate part adjacent to the first plate part and which is formed to have a space smaller than the primary air blowing space to allow some of the air of the primary air blowing space to blow.