To provide a semiconductor manufacturing device comprising a cassette chamber in which particles are prevented from being blown up without lowering the index of the device at the time of the ventilation work of the cassette chamber.

A CVD device comprising a cassette chamber 102 for delivering a cassette 7 containing a semiconductor substrate 6 to/from a chamber 4 for treating the semiconductor substrate 6 variously and varying inner pressure to a normal level or a reduced level by supplying or discharging gas is further provided with a section 103 for attracting particles 16 into the cassette chamber 102 by an electrostatic force.