PURPOSE: To realize a multi-frame synchronization circuit with simple circuit configuration entirely by in which synchronization of each frame of received data and synchronization of multi-frames are processed by a circuit of the same configuration at a receiver side with respect to the synchronization identifi cation method in which the receiver side establishes and maintains the synchroni zation of multi-frames each comprising plural frames by using a synchronization word (UW: called unique word being a 1/0 specific patterned used for communi cation of radio data in which data subjected to PSK modulation or the like are communicated.

CONSTITUTION: A transmitter side uses a multi-frame as one block to compose a frame where both unique word UW and data are inverted, and the receiver side is provided with a UW detection section 20 detecting the unique word UW and its inverted pattern the inverse of UW) and also with a detection section l detecting the change in the pattern of the unique word UW, and synchronization of the multi-frame of received data is identified depending on the detection point of time of the change in the pattern.