To provide a synthesizer reducing the frequency changeover of the frequency hopping radio equipment.

The synthesizer is provided with a D/A converter 2 operated in a switching timing based on a switching pattern of a prescribed frequency, a voltage controlled oscillator 3 operated by an output of the D/A converter 2, and a phase locked loop circuit 5. Furthermore, in the synthesizer 6 for the frequency hopping radio equipment switching in time division a transmission frequency into a reception frequency, a sample-and-hold circuit 8 is provided between the D/A converter 2 and the voltage controlled oscillator 3 and a control voltage is held by the sample-and-hold circuit 8 based on frequency data before changeover of the D/A converter 2. When the D/A converter 2 reaches the control voltage based on the frequency data after the changeover in the switching timing, the sample-and-hold circuit 8 is operated to switch the frequency of the synthesizer.