A spool braking device and a spool braking method for increasing spool braking capability. The spool braking device includes a reel attached to a fishing rod in a detachable manner. A rotatable spool is arranged in the reel. A fishing line is wound to the spool. A brake mechanism electronically brakes rotation of the spool. An acceleration sensor detects swing acceleration produced when the fishing rod is swung and generates an acceleration signal. A brake control unit determines whether or not the spool needs to be braked based on the acceleration signal and drives the brake mechanism.