A transmission mode/guard length detection circuit that uses the Orthogonal Frequency Division Multiplexing method, in which: a difference between a reference wave having a constant period generated on the basis of a transmission mode length that is a time period length of the predetermined symbol and a guard length that is a time period length of the guard interval and the peak value interval is calculated as a shift amount, and the shift amount is integrated for a symbol and is output, and the result of the integration for a predetermined symbol is changed on the basis of the shift amount.