<p>It is possible to provide a PLL device capable of obtaining significantly high frequency stability. More specifically, a standard signal is sampled from a constant temperature bath-equipped crystal oscillator (OCXO) by an A/D (analog/digital) conversion unit by using a frequency signal which is a 40 MHz rectangular wave. The digital signal is subjected to an orthogonal processing by an orthogonal conversion unit. A real part (I) and an imaginary part (Q) are acquired from a complex number of a vector of a phase equivalent to a phase difference between the standard signal and the frequency signal from the OCXO. The angular velocity of the vector is detected and a DC voltage corresponding to the angular velocity is generated via a PWM control unit and supplied to the OCXO.</p>
