A device for detecting polarization direction of a ferroelectric is provided. From a measurement signal provided through a probe disposed in contact with or near the surface of a ferroelectric, a demodulation means generates a detection signal having a signal level corresponding to a capacitance change of the ferroelectric due to application of an alternating electric field to a capacitor component formed in the ferroelectric directly below the probe. A synchronous detection means performs synchronous detection of the detection signal based on a synchronous signal and generates a polarization direction detection signal corresponding to the polarization direction of the ferroelectric. A pseudo-noise signal generation means generates a pseudo-noise signal with the same frequency as that of the electric field signal and a different phase and amplitude therefrom. The demodulation means includes a noise component removal means that removes noise components in the measurement signal through signal arithmetic processing with the pseudo-noise signal.