A signal detection circuit includes: a VCO that generates a reference signal; a complex signal generation circuit that generates a complex signal from an input signal and the reference signal; a vector operation circuit that calculates an argument of the complex signal by performing a vector operation; and a subtracting phase comparator that compares the argument with a phase of the reference signal by calculating a difference between the argument and the phase of the reference signal, wherein the complex signal generation circuit includes: a multiplication circuit that multiplies the input signal by the reference signal; and an HPF that removes a DC component from a signal output from the multiplication circuit.