PURPOSE: To reduce the thickness of a spark-advancing plate and reduce the weight and cost of the device in which spark-advancing control is carried out by relatively turning the spark-advancing plate being engaged with weights that is capable of being opened by a centrifugal force, by forming each of the long holes of the spark-advancing plate in a burr-ring shape.

CONSTITUTION: In a centrifugally spark-advancing device, while keeping balance between the centrifugal force of weights 2 due to the rotation of a shaft 1 and the tension of springs 3, each weight 2 is turned making the center of a supporting spindle 5 erectedly planted in a weight base 12 that has been fixed to the shaft 1. At that time, a spark-advancing plate 8 provided with a long hole 7 is turned by a spark-advancing pin 6 being integral with the weight 2, and finally a cam 9 being integral with the spark-advancing plate 8 is turned for controlling the timing of ignition. In this case, the long hole 7 of the spark-advancing plate 8 is formed in a burr-ring shape 11 to enhance the rigidity of the spark-advancing plate 8, and to enable the reduction in thickness thereof.