A semiconductor manufacturing method which performs reactive gas processing, wherein, when a substrate carrying system inserts a substrate from an airtight space in the substrate carrying system into a reaction chamber, and when said substrate is ejected from said reaction chamber to said airtight space, reactive gas is fed into said reaction chamber and reacts therein, the method comprising:
- a substrate carrying step of measuring the moisture content in said airtight space by means of a first moisture measuring device which is connected to said airtight space, and thereafter, inserting and ejecting said substrate by means of said substrate carrying system;
- and
- a gas processing step of performing said reactive gas processing while measuring the moisture content in said reaction chamber by means of a second moisture measuring device, which is connected to said reaction chamber, after said substrate carrying step.