A spool braking device brakes the rotation of a spool rotatably supported by a reel body. The spool, which is a conductor that is rotated in conjunction with the spool. The magnet includes an N-pole and an S-pole on a surface that faces the rotating surface of the spool. The retaining member, the support ring, and the engagement member form a magnetic flux change rate variable mechanism. The magnetic flux change rate variable mechanism varies the change rate of the flux in the rotational circumferential direction that is affected by the magnet, at a prescribed rotating surface of the spool having a prescribed unit width in the rotational axis direction, with the rotation of the spool.
