In a frequency difference calculation circuit, a first frequency difference calculation section calculates a difference between the first input frequency and an oscillation frequency of the non-integer multiple oscillation section of which an oscillation frequency is a non-integer multiple of the first input frequency. Meanwhile, a second frequency difference calculation section calculates a difference between a second input frequency in which a difference between frequency having an integer multiple of the first input frequency and the second input frequency being within a predetermined error range, and the oscillation frequency of the non-integer multiple oscillation section and an addition section calculates a difference between the first input frequency and the second input frequency adding a calculation result of the first calculation section and a calculation result of the second calculation section.