A synchronization signal detector includes a horizontal synchronization level detector, a synchronization signal extractor, a first filter circuit, and a synchronous separator. The horizontal synchronization level detector detects a horizontal synchronization detection level HL for detecting a horizontal synchronization signal from a video signal Din. The synchronization signal extractor outputs a limited signal D1 obtained by extracting only a signal within a limit range (HL−n) to (HL+m) that is set based on the horizontal synchronization detection level HL from the video signal Din. The first filter circuit removes a high frequency component of the limited signal D1 and outputs it. The synchronous separator detects a horizontal synchronization signal HS from the output signal of the first filter circuit.