Etching method and etching apparatus

An etching method of etching a coating film containing silicon formed on a substrate, comprising:

• creating a reduced pressure state inside of a processing chamber accommodating the substrate, the reduced pressure state being in a state in which a pressure is lower than atmospheric pressure;
• after creating the reduced pressure state, supplying vapor into the processing chamber;
• after creating the reduced pressure state, supplying an etching gas containing hydrogen fluoride into the processing chamber and etching the coating film formed on the substrate;
• and
• in supplying the vapor, detecting OH stretching vibration in the substrate by infrared spectroscopy, wherein
• the step of etching the coating film formed on the substrate by supplying the etching gas containing hydrogen fluoride is performed when the OH stretching vibration of a predetermined threshold value which is higher than zero is detected in the substrate.