An antenna duplexer including: a transmission filter, a reception filter, phase-shift circuits of adjusting phase characteristics on a transmission side and a reception side; and a junction point of connecting an antenna, wherein (1) an absolute value θ1 of a difference between a first phase at a predetermined frequency of a pass band of the first filter and a second phase at the predetermined frequency at the time when the reception filter side is viewed from the junction point and (2) an absolute value θ2 of a difference between a third phase at a predetermined frequency of a pass band of the reception filter and a fourth phase at the predetermined frequency at the time when the transmission filter side is viewed from the junction point is included in a range of 100 degrees or more and 170 degrees or less.