The present invention provides a high frequency generator with high accuracy in controlling the power and the phase of the output high frequency. In a high frequency generator according to an embodiment, a high frequency generated by an IQ modulation of a vector multiplier and an amplification of an amplifier is outputted through an output unit. A directional coupler outputs a first high frequencyincluding a part of traveling waves and a second high frequency including a part of reflected waves. A control unit obtains an estimated value of each of an in-phase component and an orthogonal component of the traveling waves in the output unit, and an in-phase component and an orthogonal component of the reflected waves in the output unit by performing a first matrix operation that is an operation of four polynomials, each including as multi-variables an in-phase component and an orthogonal component of a first high frequency and an in-phase component and an orthogonal component of the second high frequency. The control units determines a level of an in-phase signal and a level of an orthogonal signal that are used for IQ modulation of the vector multiplier based on the estimated values.