A local oscillator of an embodiment includes a digitally-controlled oscillator, a phase data generator, a subtractor, a loop filter, a multiplier, and a coefficient calculator. The digitally-controlled oscillator variably controls an oscillation frequency of an oscillation signal by using a first oscillator control value. The oscillation frequency is equal to a product of the first oscillator control value multiplied by an amount of change in the oscillation frequency per unit first oscillator control value. Set frequency data is calculated by dividing a set frequency by a reference frequency of a reference signal. The multiplier outputs the first oscillator control value obtained by multiplying a normalized control value from the loop filter by a first coefficient. The coefficient calculator divides, by the set frequency data, the first oscillator control value which makes the oscillation frequency roughly equal to the set frequency, and sets the quotient as a new first coefficient in the multiplier.