A vector sum phase shifter comprising: a vector summed part including an orthogonal signal generator configured to generate, from an input signal, a first signal and a second signal which are orthogonal to each other, a first variable gain amplifier configured to amplify the first signal generated by the orthogonal signal generator and generate a third signal, a second variable gain amplifier configured to amplify the second signal generated by the orthogonal signal generator and generate a fourth signal, and a signal combiner configured to combine the third signal generated by the first variable gain amplifier and the fourth signal generated by the second variable gain amplifier and output a combined signal of the third signal and the fourth signal; a table memory configured to store a relation between a control code corresponding to a phase shift amount and gains of the first and second variable gain amplifiers (13, 14); a gain controller configured to apply the gains associated with the control code to the first and second variable gain amplifiers (13, 14); a detector configured to detect amplitude and a phase from the combined signal output by the signal combiner; a recorder configured to record, when the gains are applied by the gain controller, a combination of the control code corresponding to said gains and the amplitude and the phase detected by the detector, each recorded combination forming a record; and a calibrator configured to find a phase shift characteristic of the vector summed part from the records of the recorder and calibrate the relation between a control code and gains recorded in the table memory by using the phase shift characteristic. a vector summed part including an orthogonal signal generator configured to generate, from an input signal, a first signal and a second signal which are orthogonal to each other, a first variable gain amplifier configured to amplify the first signal generated by the orthogonal signal generator and generate a third signal, a second variable gain amplifier configured to amplify the second signal generated by the orthogonal signal generator and generate a fourth signal, and a signal combiner configured to combine the third signal generated by the first variable gain amplifier and the fourth signal generated by the second variable gain amplifier and output a combined signal of the third signal and the fourth signal; an orthogonal signal generator configured to generate, from an input signal, a first signal and a second signal which are orthogonal to each other, a first variable gain amplifier configured to amplify the first signal generated by the orthogonal signal generator and generate a third signal, a second variable gain amplifier configured to amplify the second signal generated by the orthogonal signal generator and generate a fourth signal, and a signal combiner configured to combine the third signal generated by the first variable gain amplifier and the fourth signal generated by the second variable gain amplifier and output a combined signal of the third signal and the fourth signal; a table memory configured to store a relation between a control code corresponding to a phase shift amount and gains of the first and second variable gain amplifiers (13, 14); a gain controller configured to apply the gains associated with the control code to the first and second variable gain amplifiers (13, 14); a detector configured to detect amplitude and a phase from the combined signal output by the signal combiner; a recorder configured to record, when the gains are applied by the gain controller, a combination of the control code corresponding to said gains and the amplitude and the phase detected by the detector, each recorded combination forming a record; and a calibrator configured to find a phase shift characteristic of the vector summed part from the records of the recorder and calibrate the relation between a control code and gains recorded in the table memory by using the phase shift characteristic.