To provide a reference frequency generating device that can output a highly accurate reference frequency signal even if a reference signal becomes unable to be acquired. The reference frequency generating device includes a synchronization circuit, a temperature sensor, and a controller. The synchronization circuit controls a reference frequency signal outputted from a voltage controlled oscillator, by a control signal obtained based on a reference signal. The temperature detector detects a temperature of the voltage controlled oscillator being used. When the reference signal is unable to be acquired, the controller corrects a voltage controlled signal in consideration of a distortion in the aging characteristic of the voltage controlled oscillator based on a rate of change with time in a slope of the oscillator temperature, and generates a holdover control signal based on corrected contents to control the voltage controlled oscillator.