A drag knob for adjusting a drag force of a spinning reel includes a knob body, a screwable member and a rotation prevention member. The knob body includes a knob portion rotatable in a circumferential direction of the spool shaft, and an accommodating recess. The knob body protrudes forward in an axial direction and extends in a radial direction. The accommodating recess has a rearward opening in the axial direction of the spool shaft. The screwable member is disposed in the accommodating recess of the knob body and is screwed onto a front end of the spool shaft. The rotation prevention member is configured to prevent the screwable member from rotating relative to the knob body, has a width narrower than a width of the knob portion and protrudes from the screwable member in a same direction as an extending direction of the knob portion of the knob body.