A compressor includes a first muffler chamber communicating with a first cylinder chamber, and a second muffler chamber communicating with a second cylinder chamber. The first muffler chamber and the second muffler chamber are communicated with each other by a gas passage. The gas passage is communicated with a Helmholtz type resonance chamber by a connecting passage. The connecting passage is connected to a lowermost end of the resonance chamber. Therefore, oil contained in the refrigerant gas, even if having entered into the resonance chamber, is discharged through the connecting passage located at the lowermost end of the resonance chamber to outside of the resonance chamber. Thus, since oil is not accumulated in the resonance chamber, the resonance chamber keeps generally constant in capacity at all times.