A quadrature modulator includes a first switched capacitor power amplifier that amplifies a first high-frequency signal, a second switched capacitor power amplifier that amplifies a second high-frequency signal, a first combiner which includes at least one pair of winding wires, one winding wire in one pair being disposed on a primary side to which the amplified first high-frequency signal and the amplified second high-frequency signal are separately input and the other winding wire in the one pair being disposed on a secondary side, the first combiner combining the input amplified first high-frequency signal and the input amplified second high-frequency signal to generate a quadrature modulation signal from the secondary side, a first inductor disposed between the first switched capacitor power amplifier and the primary side of the first combiner, and a second inductor disposed between the second switched capacitor power amplifier and the primary side of the first combiner.