PURPOSE: To reduce art explosive sound caused by releasing the compressed air into the atmosphere by a method wherein a sound attenuating member is installed at a point confronting the air supply opening of a bulk cassette.

CONSTITUTION: An air supply device is equipped with an air supply means 21 which supplies air to a bulk cassette 4 that delivers a chip-type part fed from a bulk case to an electronic part mounting device by air, wherein a sound attenuating member 35 of continuous porous material is arranged at a point confronting the air supply opening 16 of the bulk cassette main body 4 when the air supply means 21 approaches the bulk cassette main body.