A fishing reel has a body, a spool, a handle and a warning device. The body has a spool axle rotatably mounted in the body. The spool is rotatably and coaxially mounted around the spool axle of the body. The handle is rotatably mounted on the body and is connected to the spool. The warning device is mounted between the spool and the spool axle and has at least one illuminating element, an annular coil and an annular permanent magnet. Each illuminating element is mounted through the spool. The annular coil is coaxially mounted in the spool and is electrically connected to each illuminating element. The annular permanent magnet is coaxially mounted around the spool axle, corresponds to the coil and is separated from the coil by a gap.