This phase-shift circuit (10) is equipped with a 90-degree hybrid circuit (11), variable capacitors (12, 13), a switch circuit (21), and a balun circuit (31). The 90-degree hybrid circuit (11) is equipped with a high-frequency signal input terminal (P11) and a high-frequency signal output terminal (P21). The variable capacitors (12, 13) are respectively connected between first and second variable capacitor connection terminals (P12, P22) of the hybrid circuit and ground. The balun circuit (31) is equipped with an unbalance signal input terminal and balanced signal output terminals (P(+), P(-)) comprising one pair of terminals. The switch circuit (21) selects either balanced signal output terminal (P(+)) or balanced signal output terminal (P(-)) of the balun circuit (31) and connects the terminal to the high-frequency signal input terminal (P11) of the 90-degree hybrid circuit (11).