A band-pass filter (131), which extracts a frequency component of a teletext reference signal from a digital input signal obtained by digitizing a composite signal, is provided in a frequency characteristic enhancement circuit (130). A determination circuit (145), which determines a state of the composite signal in accordance with maximum and minimum values of an output of the frequency characteristic enhancement circuit (130) during the period of the teletext reference signal and in accordance with maximum and minimum values of the output of the frequency characteristic enhancement circuit (130) during the period of time between a current horizontal synchronization interval and a next horizontal synchronization interval, is provided in a slicing circuit (140). A signal to be output to the slicing circuit (140) is generated by the frequency characteristic enhancement circuit (130) in accordance with either an output of the band-pass filter (131) or the digital input signal which is selected according to a determination result obtained by the determination circuit (145).