A communication module includes a serial resonator of a transmission filter and an auxiliary resonator of a reception filter. Each of the serial resonator and the auxiliary resonator includes a piezoelectric substrate and a positive-side comb-shaped electrode and negative-side comb-shaped electrode meshing with each other. The positive-side comb-shaped electrode in the transmission filter and the negative-side comb-shaped electrode in the reception filter are connected to each other. The orientation from the positive-side comb-shaped electrode to the negative-side comb-shaped electrode relative to the crystal orientation of the piezoelectric substrate in the transmission filter and the orientation from the negative-side comb-shaped electrode to the positive-side comb-shaped electrode relative to the crystal orientation of the piezoelectric substrate in the reception filter are inverse to each other.