A multiple frame rate synchronous detecting apparatus for synchronous-detecting received serial data having one frame rate among a plurality of predetermined frame rates is provided. The apparatus comprises a serial-to-parallel converter for serial-to-parallel converting the received serial data with matching with highest frame rate, a coincidence detector for comparing a portion of the converted parallel data corresponding to a predetermined region defined based on the frame rate, with a pattern for synchronous detection to detect coincidence, and a synchronous determiner for determining to have been synchronized with the frame rate when a periodic cycle of the coincidence detection is the same as a previous one.