A reference frequency generator device (11) is provided with a GPS receiver (21), a PLL circuit (31), a detector (28), a storage unit (29), and a control unit (22). The PLL circuit (31) controls the digital control oscillator (26) based on a synchronization control signal obtained based on a reference signal from the GPS receiver (21). In the storage unit (29), the control value of the synchronization control signal and the correspondence between the voltage value and temperature at that time are stored. When the reference signal is not obtained, the control unit (22) determines a hold-over control signal based on the correspondence and the voltage and temperature detected by the detector (28), and controls the digital control oscillator (26).