A sinker control apparatus for flat knitting machines located on a transverse board over a plurality of knitting needles to drive parallel sinkers hinged between the knitting needles to rotate. The sinker control apparatus includes a base, a linked movement portion located on the base to perform driving movements, a first control cam and a second control cam hinged on the linked movement portion, and a switching portion coupled with the linked movement portion. The switching portion includes at least one connection rod connecting to the linked movement portion, a switching seat coupled on the connection rod and an elastic element coupled around the connection rod to provide a butting force to the switching seat towards the transverse board. The switching seat has a magnetic attracting portion at one side facing the transverse board to attract the transverse board magnetically.