To provide an oscillation circuit capable of stable oscillating operation through a wideband.

This circuit is provided with a Colppits-type oscillating part 11 with a capacitor C1, a feedback capacity adjusting part 12, a tank circuit 13 and a switch control part 14, and the part 12 is provided with transistors Q2 to Q5, resistors R4 to R7 and a capacitor C2. When an oscillation frequency is low, the transistors Q2 to Q5 are turned on, and the feedback capacity of the part 11 becomes what is obtained by equivalently and parallelly connecting the capacitors C1 and C2. On the other hand, when the oscillation frequency is high the transistors Q2 to Q5 are turned off and the feedback capacity of the part 11 is fixed equivalently by only the capacitor C1. Thereby, when the oscillation frequency is low the feedback capacity is increased to execute stable oscillation operation but when the oscillation frequency is high, the feedback capacity is reduced to avoid the generation of abnormal oscillation.