There is provided a port closing device for a compressor which is fixed to a housing of the compressor by a bolt and includes a packing and a cap. The packing closes a suction port or a discharge port formed in the housing. The packing has a first end, a second end and a peripheral surface formed between the first end and the second end. The first end of the packing has a flat seal portion that is in contact with a surface of the housing surrounding the port. The cap has a holding portion that presses the peripheral surface of the packing for holding the packing, and a pressing portion that presses the second end of the packing. The pressing portion of the cap has therethrough a hole.